Introduction

Spontaneous idiopathic acute spinal subdural hematomas (SSDHs) are highly exceptional. As neurological symptoms are usually severe, rapid diagnosis with MRI is mandatory [2, 9]. In therapeutic management, the main question is whether surgical evacuation is necessary or not. We present a case of spontaneous subtotal recovery from severe paraparesis after spontaneous acute SSDH, and review the English speaking literature.

Case report

A 59-year-old man, under acetylic salicylic acid and clopidrogrel after cardiac stenting, presented with spontaneous acute left-dominant paraparesis sub T8 with an average muscle strength of M3 and severe sphincter dysfunction. Gadolinium-enhanced MRI revealed an acute SSDH from T2-9 anterior to the spinal cord (Fig. 1). No underlying tumor or vascular malformation was seen. Because of the extensive cranio-caudal hematoma extension and poor medical condition, particularly in the fear of causing postoperative recurrent subdural or epidural hematoma because of acetylic salicylic acid and clopidogrel, conservative treatment was chosen under constant readiness for surgery in case of progressive worsening. Clopidogrel was discontinued in accordance with the treating cardiologist, while aspirine was continued. Under initial bed rest and steroids, leg strength fluctuated between grades M 1–3 for 2 days and improved thereafter. Full muscle strength was regained at 1 year; ataxia, temperature/pain sensation, and urge incontinence had well improved. MRI at 5 weeks showed hematoma resorption (Fig. 2), and at 16 weeks, cystic arachnoiditis was observed with spinal cord deformity and without further re-bleedings (Fig. 3).

Fig. 1
figure 1

Sagittal T2- and T1-weighted MRI showing acute SSDH primarily anterior to the spinal cord from T2–9

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Fig. 2
figure 2

Sagittal T2-weighted MRI at 5 weeks after the acute bleeding, showing resorption of the thoracic SSDH

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Fig. 3
figure 3

Sagittal T2-weighted MRI at 16 weeks after the acute bleeding, showing cystic arachnoiditis with spinal cord deformity and without further re-bleedings

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Discussion

SSDHs are uncommon and often result from major or minor spine trauma or from spine puncture including spinal anesthesia. “Spontaneous” acute SSDHs are even more rare and have mostly been observed in conjunction with coagulopathy or anticoagulant therapy, intraspinal tumor, and vascular anomaly such as an aneurysm or dural arteriovenous fistula [3, 9, 12]. Spontaneous SSDHs without detectable structural lesion or anticoagulation are less numerous again, and we detected 16 properly documented cases in the readily available English-speaking literature (Table 1).

Table 1 Published cases of idiopathic spontaneous acute SSDH
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SSDHs are predominantly found in the thoracic spine, usually extending over several vertebral levels [2, 3, 6, 9]. Severe acute local back pain with sensorimotor deficits and sphincter disturbance are the typical clinical manifestation [3, 9, 12]. MRI is the imaging of choice; it shows the hematoma location in relation to the dura and spinal cord, its cranio-caudal extension, and usually shows or rules out an underlying tumor or AVM [9, 11, 12]. Acute SSDHs (1–3 days) are isointense on T1 and mixed on T2 images; in the subacute stage (4–7 days), they show high intensity on both T1 and T2, and diffuse high signal is seen in the chronic stage after weeks to months [9, 11]. While epidural hematomas are usually found posterior to the spinal cord in a lentiform shape, SSDHs are commonly found anterior-lateral to and around the spinal cord in a semi-circular pattern with compression and little displacement [3, 9, 11]. Angiography has been used inconsistently to rule out AVF, AVM, or aneurysm, and was performed in six of the 16 retrieved cases (Table 1). While some authors recommend spinal angiography in the presence of spontaneous SSDH whenever available [3, 12, 15], others judge that gadolinium injected MRI, particularly if repeated, should show vascular malformations directly or by flow void signals [7, 17]. Many papers do not discuss the indication for spinal angiography [1, 6, 9–11, 14], and it remains a case to case decision based on availability, degree of neurosurgical emergency, and suspicion level of vascular malformation.

The pathomechanism in spontaneous idiopathic SSDHs is little understood [2, 11]. It is commonly thought that either the hematoma originates from rupture of valveless radiculomedullary veins in the subarachnoid space after increased intra-abdominal or intra-thoracic pressure (coughing or straining) or from minor trauma and that it subsequently breaks through the thin arachnoid into the subdural space [9, 12, 15]. This hypothesis could explain clinical signs of SAH in many patients with SSDH, the reported combination of SSDH and SAH, and the potential dilution of such hematomas by the CSF [9, 12]. Conversely, SSDH has been thought to arise from the few thin, delicate extra-archnoidal vessels located on the inner dural surface and then breaking through the arachnoid into the subarachnoid space, and it is usually impossible to determine the origin [3, 7, 13]. In either case, the diluting effect of the CSF prevents clot formation, unless the hematoma is sufficiently large to block CSF flow [8, 12].

In idiopathic SSDHs, therapy is limited to the hematoma management, as there is no underlying pathology to address surgically. Platelet dysfunction has been shown to be associated with SSDH not only in our case but also in a cases with polycythemia vera [4] and essential thrombocythemia [10]. Discontinuation of anti-aggregating medication, however, must be weighed against potential thrombotic complications, and depends on the individual indication of such a treatment. Patients with mild symptoms or in poor general conditions should be treated conservatively [3, 9, 15]. There is an ongoing controversy, however, whether surgical or conservative treatment should be preferred in severe neurological deficit. While most authors advocate rapid surgical evacuation via laminectomy, posterior dural opening, and hematoma removal in such cases [6, 9, 11, 12, 15], several spontaneous recoveries have been reported in cases with moderate neurological deficits [4, 14, 17], and surgical evacuation in a large review of 106 cases with all types of SSDHs has yielded a poor outcome in 58% [2]. Kyriakides in his review concluded that “patients with incomplete neurologic deficit tend to recover with or without surgery. Patients who exhibit signs of deterioration are usually likely to benefit from percutaneous drainage or surgery” [12]. Our current case shows that substantial neurological recovery can occur even in severe paraparesis; however, we do not conclude that conservative treatment should generally be chosen in severe neurological deficit with “difficult” medical conditions. Initial conservative treatment and close observation can be a treatment option as has been shown previously for “mild” paraparesis and hemi-paresis [4, 14, 17]. Indeed, the current authors were initially not sure whether they should go for surgery in their case, but were very reluctant to do so primarily because of acetylic salicylic acid and clopidogrel.

We agree to the hypothesis that spontaneous recovery from SSDH may be explained by a progressive cranio-caudal distribution and pressure drop of the hematoma within the subdural space on one hand and dilution of the hematoma by CSF in the presence of arachnoidal tearing on the other hand [8, 12, 17]. The current case further confirms that sphincter disturbance is the least likely to be improved, as has been found before [11]. Paraplegia carries a poor prognosis even with surgery [6, 12].

In conclusion, there is a general agreement that in mild symptoms, conservative treatment is preferred in spontaneous idiopathic acute SSDH. A clear trend for surgical evacuation via laminectomy and posterior dural opening is found in the literature in cases of a severe neurological deficit; however, the current case demonstrates that good neurological recovery can occur even in severe paraparesis. Patients with paraplegia and sphincter disturbance have the poorest prognosis regardless of surgical or conservative treatment.