Arteries and Veins of the Cerebellum

Abstract

Surgery of the posterior fossa represents a technical challenge because of the proximity of the vessels of the cerebellum. If the arterial vascularization of the cerebellum is well known, the main arterial variations and the whole venous vascularization are probably under recognized. We describe the vascular organization and the main variations through photographs of colored latex perfused brains, obtained with a surgical microscope. The arterial vascularization of the cerebellum is based on three arteries which all originate from the vertebrobasilar system: the superior cerebellar artery (SCA), the anterior and inferior cerebellar artery (AICA), and the posterior and inferior cerebellar artery (PICA). The main arterial variations involve essentially the origin of these vessels. Concerning the SCA, its origin depends on the embryology. The AICA can arise from a common trunk AICA-PICA. It can be sometimes doubled and rarely absent. The PICA also can arise from a common trunk AICA-PICA and sometimes from the extradural segment of the vertebral artery. Concerning the venous organization, we distinguish the superficial and deep veins. The superficial veins drain the cerebellar cortex and transit on the surface of the cerebellum. The deep veins refer to the veins transiting in the fissures between the cerebellum and the brainstem. All these veins terminate as bridging veins that we can divide in three groups: a superior group emptying into the great vein, a posterior group emptying into the transtentorial sinus, and a lateral group ending into the superior petrosal sinus. The surgical implications are discussed.

Introduction

Surgery of the cerebellum represents a technical challenge because of the proximity of the brainstem, the cranial nerves, and the vessels in the posterior fossa. Contrary to brainstem and cranial nerves which are already well understood, a good knowledge of the vascularization of the cerebellum and its variations seems mandatory before performing surgery in this area.

Materials and Methods

Twenty-five formalin-fixed human heads were perfused with red- and blue-colored latex. Additional fixed, but non-injected, brains were used for morphological study. The brains were removed some days later, and the cerebellum was examined using a Wild Leitz surgical microscope with a D-80 Nikon photographic attachment set. We examined the arteries and veins of the cerebellum.

Anatomical Description

We start with the morphology of the cerebellum, followed by a description of the arteries and veins with particular attention paid to the vascular variations.

Reminder: Morphology of the cerebellum (anterior view, superior view, and inferior view)

The posterior cranial fossa includes the cerebellum and the brainstem. The cerebellum is attached laterally to the brainstem through the cerebellar peduncles and through the superior and inferior medullary velum which cover the fourth ventricle on the midline.

Anterior view

The anterior view allows us to reveal the cerebellopontine angle (Fig. 1). Each cerebellar hemisphere is divided by a horizontal fissure which is referred to as a horizontal fissure or petrosal fissure. Above this fissure, we can see from medially to laterally the quadrangular lobule, the simple lobule, and the superior semilunar lobule; under this fissure, from laterally to medially, we can identify the inferior semilunar lobule, the gracile lobule, the biventral lobule, and the cerebellar tonsillar partially hidden by the brainstem. The flocculus stays at the medial part of the horizontal fissure.

Fig. 1

Anterior view of the cerebellum and the brainstem. Each cerebellar hemisphere is divided by a horizontal fissure (Hf) which is referred to as a horizontal fissure or petrosal fissure. Above this fissure, we can see from medially to laterally the quadrangular lobule (Qu), the simple lobule, and the superior semilunar lobule (Se); under this fissure from laterally to medially, we can see the inferior semilunar lobule (Se), the gracile lobule, the biventral lobule (Bl), and the cerebellar tonsillar (To) partially hidden by the brainstem. The flocculus (Fl) remains at the medial part of the horizontal fissure. V fifth cranial nerve; VI sixth cranial nerve; VII seventh cranial nerve; VIII eighth cranial nerve; IX ninth cranial nerve; X tenth cranial nerve; XI eleventh cranial nerve; Ch. Pl. choroidal plexus

Laterally, we can see the apparent origin of the cranial nerves from the brainstem.

Superior view

The superior view shows the tentorial surface of the cerebellum (Fig. 2). Laterally, we find the hemisphere segmentation in lobules, as described previously, located above the horizontal fissure. In the midline, we observe vermian lobules from anterior to posterior: the lingula, the central lobule, the culmen, the declive, and the folium.

Fig. 2

Superior view of the cerebellum and the brainstem. The superior view shows the tentorial surface of the cerebellum. Laterally, we find the hemisphere segmentation in lobules above the horizontal fissure (from medially to laterally the quadrangular lobule (Qu), the simple lobule (Si), and the superior semilunar lobule (Se). In the midline, we can see vermian lobules from anterior to posterior: the lingula (Li), the central lobule (Cl), the culmen (Cu), the declive (De), and the folium (Fo). IV fourth cranial nerve; V fifth cranial nerve

Inferior view

The inferior view shows the inferior vermian lobules on the midline: from posterior to anterior folium, tuber, pyramid, and uvula (Fig. 3). Laterally, we find the hemispheric segmentation as described above and the cerebellomedullary fissure.

Fig. 3

Inferior view of the cerebellum and the brainstem. The inferior view shows the inferior vermian lobules on the midline: from posterior to anterior folium (Fo), tuber (Tu), pyramid (Py), and uvula (Uv). Laterally, we find the hemispheric segmentation (from laterally to medially the inferior semilunar lobule (Se), the gracile lobule (Gr), the biventral lobule (Bi), and the cerebellar tonsillar (To) and the cerebellomedular fissure

Arteries of the Cerebellum

We can distinguish three cerebellar arteries: the superior cerebellar artery (SCA), the anterior inferior cerebellar artery (AICA), and the posterior inferior cerebellar artery (PICA). These arteries all originate from the vertebrobasilar arterial system (Figs. 4 and 5).

Fig. 4

Anterior view of the cerebellum. The brainstem has been removed. In the middle is the fourth ventricle with its roof and on both sides is the cerebellar peduncles. The three main arterials trunks and their branches are visible: on the left superior surface, the superior cerebellar artery (SCA); on the horizontal fissure, the anterior inferior cerebellar artery (AICA); and on the inferior surface, the postero inferior cerebellar artery (PICA)

Fig. 5

Anterior view of the cerebellum and the brainstem. The optic chiasma and the Willis polygon are visible at the top of the picture and on each side the temporal poles. In this picture, we can see an example of the organization of the vertebrobasilar system. The SCA commonly arises from the basilar trunk under its division in cerebral posterior arteries. The AICA typically arises from the basilar trunk in its lower third and sometimes from the vertebrobasilar junction as on the left. The PICA arises here from the vertebral artery on the left or from an AICA-PICA on the right. III third cranial nerve; V fifth cranial nerve; VI sixth cranial nerve

SCA

The SCA is the most constant vessel and commonly arises from the basilar trunk (Figs. 6 and 7). Its origin depends on the embryology. Sometimes the SCA originates from the junction of the basilar tip and the first segment of the posterior cerebral artery (P1) (Fig. 8) or directly from P1 (Fig. 9) with a symmetrical or asymmetrical aspect [1–3].

Fig. 6

Anterior view of the tip of the basilar trunk, the brainstem, the optic chiasma, and the two internal carotid arteries (ICA). Example of bilateral cranial fusion of the posterior division of the ICA: on both sides, left and right SCA arise from the basilar artery. Ps pituirary stalk, PCA posterior cerebral artery, III third cranila nerve, VI sixth cranial nerve

Fig. 7

Anterior view of the tip of the basilar artery (BA) and inferior view of the floor of the third ventricle with the two mammillary bodies. Another example of bilateral cranial fusion of the posterior division of the ICA: on both sides, left and right SCA arise from the basilar artery. III third cranial nerve; PCoA posterior communicating artery

Fig. 8

Anterior view of the tip of the basilar trunk (BA), the brainstem, the optic chiasma, and the Willis polygon and inferior view of the floor of the third ventricle with the two mammillary bodies. Example of symmetrical caudal fusion: the two SCA arise from the junction of the tip of the basilar artery and the first segment of the posterior cerebral artery (PCA) shaping a “quadrifurcation”. PCoA posterior communicating artery

Fig. 9

Anterior view of the tip of the basilar trunk, the brainstem, the optic chiasma, and the Willis polygon and inferior view of the floor of the third ventricle with the two mammillary bodies and the pituitary stalk. Example of left partial caudal fusion, on the left two SCA, arises from the P1 segment of the PCA. Ps pituitary stalk, III third cranial nerve

The aspect of the basilar tip depends on the site of fusion of the posterior division of the ICA. The more caudal the fusion is, the more frequent the duplicate origin of the SCA becomes (Fig. 10).

Fig. 10

Anterior view of the tip of the basilar trunk, the brainstem, the optic chiasma, and the Willis polygon and inferior view of the floor of the third ventricle with the two mammillary bodies and the pituitary stalk. Example of bilateral caudal fusion, a double SCA, appears on each side. III third cranial nerve, Ps pituitary stalk

When the SCA originates from the basilar artery, it passes below the third cranial nerve, and when it comes from P1, it can pass above the oculomotor nerve [3]. Classically, the SCA transits under the third cranial nerve and the fourth cranial nerve before joining the lateral side of the pontomesencephalic junction (Figs. 5 and 6). After crossing the trigeminal nerve, above or under, the SCA splits into two branches: the medial and the lateral branches which transit along the free edge of the tentorium. Both these arteries join the cerebellomesencephalic fissure (Fig. 11).

Fig. 11

Right lateral view of the mesencephalon, the pons, and the right cerebellar hemisphere. The SCA divides into two branches and the medial branch (cranial) divides into two branches: the medial for the mesencephalon and the lateral for the vermis and the superomedial hemispheric cortex. The lateral branch vascularizes the cerebellar cortex and the dentate nucleus. It can make some contribution to the other deep nuclei (globulus, emboliform, and fastigial). The pontotrigeminal vein combines with the cerebellopontine fissure, receives the superior hemispheric vein, and passes above the fifth cranial nerve (Trn) before reaching the anterior hemispheric vein in the superior petrous vein (SPV). IV fourth cranial nerve; VII seventh cranial nerve; VIII eighth cranial nerve

The medial branch leads to two branches: a medial branch for the mesencephalon, the superior and inferior colliculi and the cerebellar cortex, and a lateral branch for the vermis and the superolateral cortex of the cerebellar hemisphere (Figs. 12, 13, and 14).

Fig. 12

Left latero superior view of a half left mesencephalon and half left cerebellum showing the basilar tip with the left SCA dividing into medial and lateral branches. The mesencephalon and the colliculi are supplied by a medial branch of the medial branch of the SCA. There is a tectal network involving the collicular arteries arising from the SCA trunk and tiny branches originating in the medial branch of the SCA. The trochlear nerve (Tn) loops around the mesencephalon

Fig. 13

Superior view of the mesencephalon and the cerebellum. The tip of the basilar trunk is sectioned just under the origin of the PCA. The SCA divides into two branches: medial and lateral. The medial one splits into two other branches. The first one for the mesencephalon and colliculi and the other for the vermis and superomedial hemispheric cerebellar cortex. The lateral branch vascularizes the superior cerebellar hemispheric cortex

Fig. 14

Right lateral view of the tentorial surface of the right cerebellar hemisphere and the right lateral aspect of the mesencephalon. The lateral division of the SCA (asterisk) essentially supplies the superior hemispheric cortex but also the tegmen ponti and the dentate nucleus. There is a marginal artery for the hemispheric cerebellar hemisphere. III third cranial nerve, IV fourth cranial nerve, TTS transtentorial sinus

The medial branch vascularises by descending branches, the superior vermis and the neighboring part of the surface of the cerebellar hemisphere; it also sends rami running along the superior cerebellar peduncles and reaching the dentate nucleus and can contribute to some other deep nuclei (globulus, emboliform, and fastigial) (Figs. 13, 14, and 15).

Fig. 15

Tentorial surface of the cerebellum. The vermian branches come from the lateral branch of the medial branch of the SCA. The superior hemispheric vascularization comes from the lateral branch of the SCA

The lateral branch vascularises the most lateral part of the superior cerebellar cortex, i.e., the quadrangular, simple, and semilunar lobules (Fig. 16). The perforating arteries supplying the deep nuclei can arise from the SCA main trunk, but also from the medial and lateral branches of the first division.

Fig. 16

Horizontal anatomical slice of the cerebellum passing through the dentate nucleus (Dn). The dentate nucleus is vascularized by a rami of the medial branch of the SCA

It is important to notice that there are some anastomosis between the SCA and the AICA (Fig. 14) and between the SCA and the PICA as described below.

Aica

The AICA arise from the basilar trunk in 99 % of cases and classically from the lower third (75 % of cases). It can also arise close to the vertebrobasilar junction in 9 % of cases (Fig. 5).

This vessel is also called the cerebellolabyrinthine artery because it gives off the labyrinthine artery in 90 % of cases [1–6].

Sometimes we may observe a common trunk for AICA and PICA arising from the basilar artery (Fig. 17). There is often also an accessory PICA (Fig. 17) or accessory AICA (Fig. 18).

Fig. 17

Anterior view of the right part of the vertebrobasilar system. There is common trunk AICA-PICA. The trunk divides in a real AICA and PICA. The AICA runs backwards from the sixth cranial nerve (VI). There is an accessory PICA (asterisk). V fifth cranial nerve, VII–VIII facial and cochleovestibular nerves

Fig. 18

Anterior view of the left part of the vertebro basilar system. There is an AICA and a PICA arising from the basilar trunk. V fifth cranial nerve, VII–VIII facial and cochleovestibular nerves

Rarely, there is no AICA (4 % of cases): the AICA comes from a common trunk arising from the vertebral artery or directly from the PICA (Fig. 19).

Fig. 19

Anterior view of a vertebro basilar system. In this case, there is no right AICA originating from the basilar artery. The AICA originates directly from the PICA. VI sixth cranial nerve, VII–VIII facial and cochleovestibular nerves

In some cases, there is a duplicate AICA with a small branch giving off the labyrinthine artery and the vascularisation of the flocculus and a larger branch supplying the semilunar and biventral lobule (Fig. 20).

Fig. 20

Anterior view of the vertebro basilar system showing a duplicate AICA with a small branch (single asterisk) giving off the labyrinthine artery and the vascularisation of the flocculus and a larger branch (double asterisk) supplying the tonsillo-hemispheric territory of the PICA. VI sixth cranial nerve, VII–VIII facial and cochleovestibular nerves

The AICA transits then above or below the sixth nerve. It can perforate the sixth nerve or passes between two rootlets of the nerve (Fig. 21).

Fig. 21

Anterior view of the vertebro basilar junction. The right AICA perforates the sixth cranial nerve. The right PICA transits under the twelfth cranial nerve. Vertebral artery (VA), basilar artery (BA)

After crossing the sixth nerve, AICA joins the cerebellopontine angle and the facial and cochleovestibular nerves.

It can also pass between [7] (Fig. 22), below (Fig. 23) or above (Fig. 24), the facial and cochleovestibular nerves.

Fig. 22

Superior view of the right cerebellopontine angle. The posterior side of the petrous bone is on the right of the picture. On the left, we can see the superior petrous vein (SPV) and the fifth cranial nerve (Trn) arising from the brainstem. At the bottom, we locate the facial (Fn) and cochleovestibular nerves. The AICA usually passes between these two nerves

Fig. 23

Superior view of the right cerebellopontine angle focusing on the internal acoustic meatus. In this case, the AICA passes under the facial (Fn) and vestibulocochlear nerves. V fifth cranial nerve

Fig. 24

Postero superior view of the right cerebellopontine angle focusing on the internal acoustic meatus. In this case, the AICA transits above the facial and cochleovestibular nerves and produces the labyrinthine artery and the subarcuate artery. Fn facial nerve

At this level, the AICA gives off the labyrinthine and the subarcuate arteries. The labyrinthine artery follows and supplies the vestibulocochlear and the facial nerves (Fig. 25). It enters the internal auditory canal and terminates by giving rise to vestibular, cochlear and vestibulocochlear arteries.

Fig. 25

Anterior view of the apparent origin of the left facial (Fn) and cochleovestibular nerves arising from the medullo pontine sulcus. The AICA produces the labyrinthine artery (asterisk) but also small vessels for the flocculus. Fn facial nerve

The AICA then bifurcates into two branches. The bifurcation takes place before (in two-thirds of cases) or after (in one-third of cases) crossing the facial and cochleovestibular nerves [3]. We distinguish the rostrolateral branch and the caudomedial branch (Fig. 26).

Fig. 26

Anterior view of the brainstem and the petrous surface of the right cerebellar hemisphere. The AICA comes from the basilar artery and combines with the area of the horizontal fissure. At the level of the facial and cochleovestibular nerves (Fn), the AICA divides into two branches: The rostro lateral branch transits laterally above the horizontal fissure and above the flocullus but under the cochleovestibular and facial nerves, before combining with the superior lip of the cerebellopontine fissure. The caudo medial branch transits below the flocculus and produces cortical branches for the petrosal surface around the horizontal fissure. It penetrates the inferior cerebello medullar fissure where it transits along the foramen of lushka and then returns to the anterior petrosal surface of the cerebellar hemisphere

The rostrolateral branch transits laterally above the horizontal fissure and the flocullus in front of the middle cerebellar peduncle, before combining with the superior lip of the cerebellopontine fissure and the adjacent petrosal cerebellar surface (Fig. 26).

The caudo medial branch transits below the flocculus and gives off cortical branches for the petrosal surface around the horizontal fissure. It then penetrates in the inferior cerebello medullary fissure where it transits along the foramen of Lushka and then goes back on to the anterior petrosal surface of the cerebellar hemisphere ending by giving rise to cortical arteries (Fig. 26).

The AICA usually supplies the anterior surface of the simple, superior, and inferior semilunar lobules as well as the flocculus, the choroid plexuses of the lateral ventricular recess, and the middle cerebellar peduncle; in fact, as we have seen above, its caliber as well its cerebellar vascular territory are quite variable.

We typically notice some anastomoses between the rostral branch and the SCA and between the caudal branch and the PICA.

We can see a lack of division in some cases (Fig. 27). In this case, the AICA transits along the horizontal fissure.

Fig. 27

Anterior view of the brainstem and the vertebro basilar system. In this case, there is no division of the AICA. It transits along the horizontal fissure

Pica

The PICA usually stems from the vertebral artery 2 cm from the vertebral artery dural entrance (Fig. 28). The origin of the PICA is in reality variable: it can arise from a common trunk AICA-PICA of the basilar artery (as described above), from the extradural vertebral artery at the level of C1–C2 (or even C2–C3), from the ascending phayngeal artery, and from the proatlantal artery or from the ascending cervical artery [1–4, 8–16].

Fig. 28

Anterior view of the brainstem and the vertebrobasilar system. The right PICA arises from the vertebral artery and give a PICA. On the left, a C1–C2 PICA and an AICA-PICA

The PICA crosses the last cranial nerves, passing above, between, under, or through the ninth, tenth, eleventh, and twelfth cranial nerves [9] (Figs. 21 and 29).

Fig. 29

Posterior view of the left cerebellopontine angle focused on the jugular foramen. The PICA here transiting between the tenth and the eleventh (XI) cranial nerves. Vertebral artery (VA), ninth cranial nerve (IX)

At this level, the PICA gives rise to perforating branches for the lateral part of the medulla and the olive, sharing the area with the branches coming from the basilar artery, the AICA, and the vertebral artery. It is important to note that there are no perforators arising from the vertebral artery before the PICA origin (Fig. 30), except in the case of common AICA-PICA, or extradural PICA in which the VA gives off the perforators for the anterior and lateral aspect of the medulla (Fig. 31).

Fig. 30

Anterior view of the brainstem and the vertebro basilar system. In this case, the PICA originates from the vertebral artery. Above the emerging PICA, there are some perforators coming from the vertebral artery, the basilar artery, and the PICA. Under the emerging PICA, there are no medulla perforators

Fig. 31

Left lateral view of the brainstem and the two vertebral arteries. In this case, the PICA originates from a common trunk AICA-PICA from the basilar artery. The vertebral artery (VA) produces a huge perforator for the anterior and lateral aspects of the medulla

After crossing the last cranial nerves, the PICA transits on the lateral aspect of the medulla and in front of the anterior surface of the tonsilla, before describing its first caudal loop (Fig. 32). Sometimes, the first caudal loop is very extended and overflows significantly within the cisterna magna (Figs. 33 and 34).

Fig. 32

Right lateral view of the brainstem showing the PICA originating from the vertebral artery. We can clearly see that there is no medulla perforator under the emerging PICA. The PICA crosses the lateral aspect of the medulla medially to the spinal part of the accessory nerve. It describes an intital caudal loop at the anterior surface of the tonsilla (the tonsilla has been removed here). It then follows an ascending course between the tonsilla and the dorsal surface of the medulla

Fig. 33

Posterior view of the cerebellum and the medulla. In this case, the right PICA describes a long loop in the cisterna magna. On both sides, lateral spinal arteries transit between the rootlets of the cervical spinal nerves

Fig. 34

Posterior view of the cerebellum and the medulla. The cisterna magna (CM) is intact. Through the arachnoid, we can see the first caudal loop of the PICA. The veinous drainage of the inferior posterior side of the cerebellum depends on the inferior hemispheric vein and the inferior vermian vein. Sometimes, the inferior hemispheric vein combines with the vermian vein. Inferior hemispheric vein (IHV)

The PICA then follows an ascending vertical route between the tonsilla and the dorsal surface of the medulla and reaches the superior medullary velum and the choroid plexus where it makes a second loop. It gives at this point the choroidal artery which supplies the tela choroidea and the choroid plexus (Fig. 35).

Fig. 35

Posterior view of the medulla with the choroid tela of the fourth ventricle. The PICA after its first caudal loop between the lateral side of the medulla and the spinal part of the accessory nerve follows an ascending route on the dorsal surface of the medulla and reaches the superior medullary velum and choroid plexus where it makes its second cranial loop

After this second loop, the PICA bifurcates into two branches on the medial side of the tonsilla (Fig. 36): the vermian branch (vermian trunk) for pyramid, uvula, nodule, and inferior part of the biventral lobule; and the tonsillo hemispheric branch (lateral trunk) for the superior part of the biventral lobule, the inferior part of the semilunar lobule and the tonsilla. The vermis can be vascularised bilaterally by the same PICA if the controlateral supplier is a common trunk AICA-PICA.

Fig. 36

Medial view of the right cerebellar tonsillar, the fourth ventricle and its floor. The PICA comes from the lateral side of the medulla, describes an initial caudal loop, and transits vertically between the dorsal surface of the medulla and the anterior surface of the tonsillar. At the level of the medullary velum, it describes its second loop and divides into two branches: the tonsillo vermian branch and the tonsillo hemispheric branch. The PICA supplies the tonsillar, the biventral lobe, the gracile lobe, the nucleus, and the inferior part of the semilunar lobe. It may also supply the emboliform and globulus nuclei and sometimes makes a contribution to the dentate nucleus

Tonsillo hemispheric branches and vermian branches terminate their transit on the cerebellar cortex (Figs. 4 and 37). The vermian cortical branches arise from the medial trunk and the tonsilar and hemispheric branches arise from the lateral trunk.

Fig. 37

Postero inferior view of the cerebellum and the medulla. The inferior part of the vermis is vascularized by the medial vermian branches (tonsillo vermian) of the PICA, while the inferior part of the cerebellar hemispheres is vascularized by the lateral hemispheric branches (tonsillo hemispheric) of the PICA

The cortical arteries originating from PICA establish anastomosis with the cortical branches of the SCA (Fig. 38).

Fig. 38

Posterior view of the cerebellum. There are many cortical hemispheric and vermian anastomosis between branches arising from the PICA and SCA

Veins of the Cerebellum

We can describe two groups of veins: the superficial veins, which drain the cortical surface of the cerebellum, and the deep veins. All these veins terminate as bridging veins [2, 17, 18].

Superficial Veins

Tentorial surface

The superior cortical surface of the cerebellum is drained by the superior vermian veins and the superior hemispheric veins (Figs. 39 and 40). These veins empty into the great vein of Galen in the midline (Fig. 39) and in the transtentorial medial and lateral sinuses laterally which combine with the transverse and straight sinus (Figs. 41 and 42). The transtentorial sinus also drains the inferior surface of the temporal and occipital lobe (Fig. 42). From their cortical route to the transtentorial sinuses, the superior hemispheric veins form bridging veins (Fig. 41).

Fig. 39

Superior view of the mesencephalon, the tentorial surface of the cerebellum, and the two cerebellopontine angles including the fifth (Trn), seventh, and eighth (Fn) cranial nerves. On the midline, the superior aspect of the vermis is drained by the vermian vein (VV), which terminates in the great vein of Galen, and laterally, the superior sides of the cerebellar hemispheres are drained by the superior hemispheric veins (SHV), which terminate in the transtentorial sinuses (TTS). On both sides of the mesencephalon, we can see the two superior petrous veins (SPV), draining the anterosuperior cortical surface of the cerebellum and the brainstem. These veins terminate in the superior petrosal sinus. Considering the superior aspect of the cerebellum, we observe three main axis of drainage: superior through the great vein (of Galen), lateral through the superior petrosal veins, and posterior through the transtentorial sinuses

Fig. 40

Superior view of the left cerebellar hemisphere. Sometimes, there are two superior hemispheric veins (SHV) draining the superior hemispheric surface of the cerebellar hemisphere and combining with the transtentorial sinuses

Fig. 41

Lateral view of the right superior hemispheric surface of the cerebellum. The tent is maintained towards the top, revealing a superior hemispheric vein (SHV) shaping a bridging vein before combining with the transtentorial sinus (TTS) to terminate in the lateral and straight sinuses

Fig. 42

Inferior view of the tent, the temporal and occipital lobes, and the veins of the Galen group. Laterally, we can see transtentorial sinus draining the inferior aspect of occipital and temporal lobes but also the superior aspect of the cerebellum. On the midline, we can identify the great vein of Galen (GVG), the straight sinus (SS), and laterally, the transtentorial sinus (TTS) coming from the superior hemispheric vein (SHV)

Suboccipital surface

The posterior inferior cortical surface of the cerebellum is drained by the inferior hemispheric veins and the inferior vermian veins. The hemispheric veins do not empty directly in the transverse sinus but via the transtentorial sinuses (Fig. 43). The inferior vermian veins typically empty in the straight sinus directly or via the medial transtentorial sinuses (Fig. 44). The inferior hemispheric vein can also combine with the inferior vermian veins before together merging with the straight sinus (Figs. 34 and 45). All these veins form bridging veins too.

Fig. 43

Posterior view of cerebellar cortex. On both sides, there are inferior hemispheric veins (IHV) ending in lateral and medial transtentorial sinuses, and never directly in the straight or lateral sinuses (LS)

Fig. 44

Posterior view of the cerebellar cortex after magnification: the inferior vermian veins (IVV) terminate directly in the straight sinus (SS). Lateral sinus (LS)

Fig. 45

Right posterior inferior view of the cerebellar hemisphere focused on the tonsillar. We can see the anterior tonsilar vein (ATV) and posterior tonsillar vein (PTV) and the inferior hemispheric vein (IHV) reaching the inferior vermian vein (IVV)

Petrosal surface

The anterior cortical surface of the cerebellum is drained by the anterior hemispheric veins (AHV) (Figs. 46, 47, 48, and 49). We distinguish the middle AHVs which drain the cortex of the horizontal fissure, the inferior AHVs which drains the inferior part of the petrosal surface, and the superior AHVs which drain the superior part of the petrosal surface. These veins converge in the cerebellopontine fissure and in front of the middle cerebellar peduncle to form the vein of the cerebellopontine fissure. In this area, it receives the venous drainage from the brainstem through the vein of the middle cerebellar peduncle before combining with the superior petrosal vein (Figs. 49 and 50). The superior petrosal vein then empties in the superior petrosal sinus, also forming a bridging vein (Fig. 50).

Fig. 46

Anterior view of the brainstem and the right hemisphere. The middle anterior hemispheric vein (AHV) drains the cortex of the horizontal fissure and transits as far as the cerebellopontine fissure to form with the vein of the middle cerebellar peduncle (Vmcp), the vein of the cerebellopontine fissure. This vessel receives the venous drainage from the cerebellum through the superior, middle, and inferior anterior hemispheric veins and the vein of the cerebellomedullary fissure but also the venous drainage of the brainstem through the transverse pontine vein (tpV) and the transverse medullary vein. All these vessels empty into the superior petrous vein

Fig. 47

Anterior view of the brainstem and the right hemisphere of another specimen. The anterior hemispheric vein (AHV) receives the transverse pontine and medullary veins and combines with the vein of the middle cerebellar peduncle (Vmcp) to form the vein of the cerebellopontine fissure. The vein of the middle cerebellar peduncle (Vmcp) comes from the fusion of the vein of the pontomedullary sulcus with the lateral medullary vein or the vein of the inferior cerebellar peduncle

Fig. 48

Left anterior lateral view of the brainstem and the left cerebellar hemisphere. The transverse pontine, the transverse medullary, and the anterior hemispheric veins empty into the superior petrous vein (SPV). This collector also drains the petrous and the superior cortical surfaces of the cerebellum and the brainstem

Fig. 49

Anterior view of the petrous surface of the cerebellum and the anterior side of the brainstem. The vein of the horizontal fissure (HFv) transits through the rootlets of the trigeminal nerve to reach the superior petrous vein (SPV). Basilar artery (BA)

Fig. 50

Superior view of the right cerebellopontine angle. The superior petrous (SPV) vein receives the transverse pontine vein (TPV), which transits here above the fifth cranial nerve (Trn), a posterior pontine or tectal vein and posterolaterally some anterior hemispheric veins. Superior cerebellar artery (SCA), trochlear nerve (Tn)

The superior petrosal vein can be duplicated with a medial superior petrosal vein draining the brainstem and a lateral superior petrosal vein draining the cerebellum (Fig. 51).

Fig. 51

Parasagittal anatomical section passing through the right petrous bone and the trigeminal cavum including the fifth cranial nerve (Trn). On the posterior edge of the petrous bone, we can see the internal acoustic meatus (IAM) with the facial (Fn) and cochleovestibular nerves. Below, there is the jugular foramen (JF) and the IX, X, and XI nerves. The superior petrous vein (SPV) can be doubled with a medial vein draining the brainstem and a lateral vein draining the cerebellum

Deep Veins

We use the term deep veins to refer to the veins transiting in the fissures between the brainstem and the cerebellum. We distinguish three groups of deep veins: the veins of the cerebellomesencephalic fissure, the veins of the cerebellopontine fissure, and the veins of the cerebello medullary fissure.

Veins Transiting in the Cerebellomesencephalic Fissure

We distinguish two groups of veins transiting in the cerebellomesencephalic fissure: the superomedial empties into the great vein of Galen and the superolateral empties into the superior petrosal vein. These two venous drainage groups are connected by the lateromesencephalic vein (Fig. 52).

Fig. 52

Right lateral view of the brainstem including the mesencephalon and the pons. There is a duplicate SCA with a horizontal course. The superior petrous vein is just behind the emergence of the fifth cranial nerve (Trn). The basal vein (BV) has a horizontal course at the top of the picture. These two veins communicate through the lateromesencephalic vein

The superomedial group is made up of the vein of the superior cerebellar peduncle and the supra cerebellar veins.

The vein of the superior cerebellar peduncle arises from the superior cerebellar peduncle and transits along the lateral face of the lingula. It then becomes the vein of the cerebellomesencephalic fissure (Fig. 53) and empties into the vein of Galen or into the superior vermian vein (Fig. 53).

Fig. 53

Sagittal section passing through the cerebellomesencephalic fissure. We can identify the tectal plate (TP), the lingula (Li), the culmen (Cu), and the central lobe (Cl) of the vermis. The vein of the superior cerebellar peduncle becomes the vein of the cerebellomesencephalic fissure (Vcmf), which empties into the great vein of Galen

The group of supracerebellar veins is made up of the tectal vein, the superior vermian vein, the culminal vein, the central veins which drain the superior part of the vermis, and the tectum (Figs. 54, 55, and 14).

Fig. 54

Sagittal section passing through the third ventricle (V3) and the pineal region. There is a supracerebellar group of deep veins including the tectal vein, the superior vermian vein, the culminal vein, the central veins which drain the superior part of the vermis, and the tectum. These veins terminate in the great vein of Galen (GVG) as the internal cerebral veins

Fig. 55

Superior lateral view of the vermis and the great vein of Galen (GVG) under the splenium of the corpus callosum and behind the tectum. The great vein of Galen receives the basal veins (BV) and the internal cerebral veins (ICV). It also drains the superior vermian vein, the vein of the cerebellomesencephalic fissure, the culminal vein, and the central vein. Straight sinus (SS)

The pontotrigeminal vein represents the superolateral group.

This vein transits along the superior cerebellar peduncle, passes above the trigeminal nerve, and combines with the vein of the cerebellopontine fissure to form the superior petrosal vein before terminating in the superior petrosal sinus (Fig. 11). Before the junction, it receives the superior hemispheric vein. There are often anastomoses between the ponto trigeminal vein and the lateromesencephalic vein on the medial extremity.

Veins Coursing in the Cerebellopontine Fissure

We distinguish two veins traveling along the cerebellopontine fissure:

The vein of the cerebellopontine fissure drains the petrosal surface of the cerebellum and comes from the junction of the stems of the anterior hemispheric vein. It drains into the superior petrosal sinus through the superior petrous vein. This vein can often be joined by the vein of the middle cerebellar peduncle and the ponto trigeminal vein to form a trunk that drains into the superior petrosal vein (Figs. 46, 47, 56).

Fig. 56

Antero lateral view of the pons and the left petrous surface of the left cerebellar hemisphere. The vein of the middle cerebellar peduncle transits on the anterior surface of the middle cerebellar peduncle and combines with the anterior hemispheric vein to form the vein of the cerebellopontine fissure (Vcpf). This vein combine with the ponto trigeminal vein (PTV) and the transverse pontine vein (TPV) before reaching the superior petrous vein

The vein of the middle cerebellar peduncle comes from the fusion of the vein of the pontomedullary sulcus and the lateral medullary vein or the vein of the inferior cerebellar peduncle. It then transits along the lateral sides of the middle cerebellar peduncle, in the anterior part of the cerebellopontine fissure. It drains directly into the superior petrosal sinus or combines with other stems like the vein of the cerebellopontine fissure before together draining into the superior petrosal sinus (Figs. 47 and 56).

Veins Coursing in the Cerebello Medullary Fissure

We can distinguish the vein of the cerebellomedullary fissure and the vein of the inferior cerebellar peduncle.

The vein of the cerebello medullary fissure comes from the lateral side of the uvula of the vermis and transits along the junction of the inferior medullary velum and the tela choroidea, then under the lateral recesses of the fourth ventricle as far as the cerebellopontine angle (Figs. 57 and 58). This vein drains the inferior aspect of the cerebellum and notably the dentate nucleus (Fig. 59). It then merges with the transverse medullary vein and terminates in the anterior hemispheric vein (Fig. 60).

Fig. 57

Posterior view of the medulla and the fourth ventricle. The cerebellum has been partially resected. We can see the inferior medullary velum and the choroid tela delimiting the roof of the fourth ventricle. On both sides, the cerebellomedullary fissure is located between the insertion of the medullary velum and the cerebellum. There are the two PICA executing their caudal and cranial loops and laying on the roof of the fourth ventricle. The vein of the cerebellomedullary fissure (Vcmf) stems from the lateral side of the uvula, transits in the fissure along the insertion of the medullary velum laterally to the PICA, and passes under the lateral recesses before joining the cerebellopontine angle. It receives the vein of the inferior cerebellar peduncle (Vicp)

Fig. 58

Posterior view of the inferior cerebellum and the medulla. On the midline, there is the median posterior medullary vein (mpmV) establishing anastomoses with the vein of the inferior cerebellar peduncle. These two veins empty into an occipito marginal sinus around the jugular foramen by shaping a bridging vein

Fig. 59

Horizontal section of the cerebellum and the brainstem passing through the inferior part of the fourth ventricle and the dentate nuclei with the vein of the cerebellomedullary fissure (Vcmf) draining the right dentate nucleus (Dn)

Fig. 60

Anterior view of the brainstem and the left cerebellar hemisphere. The vein of the cerebellomedullary fissure (Vcmf) merges with the transverse medullary vein (TMV) and terminates in the anterior hemispheric vein (AHV)

The vein of the inferior cerebellar peduncle transits along the inferior cerebellar peduncle. It comes from the posterior side of the medulla laterally to the foramen of Magendie. It passes below the lateral recesses and combines with the vein of the cerebellomedullary fissure (Figure 57). Inferiorly, the veins of the inferior cerebellar peduncle from each side may create anastomoses with the median posterior medullary vein by merging on the midline under the foramen of Magendie. The median posterior medullary vein can also create anastomoses with sinus converging on the jugular foramen or in an occipito marginal sinus through a bridging vein (Fig. 58).

Bridging Veins

All the veins of the cerebellum terminate as bridging veins which we can classify in three groups: a superior group emptying into the great vein (vein of Galen), a posterior group emptying into the transtentorial sinus, and a lateral group ending in the superior petrosal sinus (Figs. 39 and 42).

Discussion

As discussion, we propose to clarify some points concerning the anatomical variations of the cerebellar arterial vascularization and the technical aspect from the venous point of view for the posterior fossa approach.

We point out the variability of the arterial cerebellar vascularization concerning the deep nuclei and the cortex.

The medial branch of the SCA classically supplies the dentate nucleus which can also receive tributaries from the PICA; on the other hand, the PICA vascularises some other deep nuclei (globulus, emboliform, and fastigial) to which the SCA can also make contributions.

The lateral branch of the SCA vascularises the most lateral part of the superior cerebellar cortex (quadrangular, simple, and semilunar lobules) in balance with the AICA and the PICA.

Each half of the inferior part of the vermis is supplied by its homolateral PICA but the whole of the vermis can be supplied by one PICA if the contralateral PICA is an AICA-PICA.

Cerebellar veins have huge anastomosis on the cerebellar surface with possibilities for example of inferior vermian veins draining superiorly towards the trans tentorial sinuses and the tent with the superior vermian and hemispheric veins or inferior hemispheric cerebellar veins draining laterally and anteriorly towards the superior petrosal vein. From a surgical point of view, a good knowledge of veins is also absolutely necessary for the posterior fossa approach, firstly, to avoid a massive hemorrhage by a lesion of the bridging veins draining notably the superior hemispheric and superior vermian veins which can be torn off during a supracerebellar approach, as well as the transtentorial sinuses in a transtentorial approach.

For the supracerebellar approach, the superior hemispheric and vermian veins must be coagulated along the tent to protect the venous anastomosis on the cerebellar surface and avoid a venous infarct.

During pontocerebellar angle surgery, it’s better to protect the petrosal vein which obviously drains the brainstem and the cerebellum but also the supratentorial brain via the lateromesencephalic vein when the last part of the basal vein of Rosenthal is missing.

Conclusion

If the arterial vascularization of the cerebellum is usually well known by neurosurgeons, the main arterial variations and the whole venous vascularization are probably insufficiently recognized. Nevertheless, these notions are essential for operating in this area and notably in case of cisternal and ventricular surgery, where the main arterial trunks and bridging veins are localized.