Neurology India Medknow Publications on behalf of the Neurological Society of India ISSN: 0028-3886 EISSN: 1998-4022 Vol. 58, Num. 6, 2010, pp. 945-948

Neurology India, Vol. 58, No. 6, November-December, 2010, pp. 945-948

Case Report

Posttraumatic retroclival acute subdural hematoma: Report of two cases and review of literature

Krishnamurthy Sridhar, Prasanna G Venkateswara, Sridhar Ramakrishnaiah, Vijay Iyer

Department of Neurosurgery, Fortis Malar Hospital, Chennai, India
Correspondence Address: Krishnamurthy Sridhar, Department of Neurosurgery, Fortis Malar Hospital, 52, I Main Road, Gandhi Nagar, Adyar, Chennai - 600 020, India, neuro_sridhar@hotmail.com

Date of Acceptance: 17-Aug-2010

Code Number: ni10263

PMID: 21150065
DOI: 10.4103/0028-3886.73756

Abstract

Keywords: Acute subdural hematoma, bridging veins, posterior fossa, retroclival, trauma

Introduction

Traumatic hematomas of the posterior fossa are uncommon, seen in only about 3% of all computer tomography (CT) scans taken for head injuries. ^[1] Hematomas located in the retroclival region are rare, with a majority being pediatric epidural hematomas. Traumatic retroclival acute subdural hematomas (RSDHs) have been described earlier in only two patients. ^[2],[3] Being rare and due to their strategic location, they present to the clinician with a challenge in diagnosis and management.

Case Reports

Case 1

An 18-year-old man presented following a fall from a two - wheeler. There was history of loss of consciousness, but no seizures. On admission, he had a Glasgow Coma Score (GCS) score of 15, with no neurological deficits. A CT scan brain plain study revealed a RSDH extending to the foramen magnum [[Figure - 1]a, b]. There were no fractures of the skull base. X-rays of the cervical spine were normal. An magnetic resonance imaging (MRI) with MR-angiography was performed, which confirmed the presence of RSDH extending from near the top of the clivus, down to the anterior margin of the foramen magnum and further extending into the upper cervical canal, with no attendant vascular malformation [[Figure - 1]c, d]. There was a thin layer of acute subdural hematoma (SDH) along the posterior margin of the craniovertebral junction. There was no hydrocephalus.

Patient was initially managed expectantly. Within 24 hours, he developed bilateral sixth nerve palsies with symptoms of raised intracranial pressure, though his GCS score remained 15. A right-sided far lateral approach was used for the surgery, with subtotal evacuation of the RSDH and decompression of brainstem and cranial nerves [Figure - 2]. The patient improved gradually in his sixth nerve status. A postoperative CT scan taken 1 week after the surgery showed complete resolution of the hematoma [Figure - 3]. The patient was discharged without any neurological deficits and on follow-up at 6 months is doing well.

Case 2

A 19-year-old man presented following a fall from a moving bus. He complained of headache and neck pain. He had no neurological deficits, and his GCS score was 15. CT scan brain showed an RSDH extending from the top of the clivus to the level of C1 [[Figure - 4]a, b]. There were no fractures of the skull, and x-rays of the cervical spine were normal. A digital subtraction angiography (DSA) did not reveal any evidence of aneurysm or vascular malformation. MRI brain confirmed an RSDH [[Figure - 4]c, d]. He was managed symptomatically. He was discharged after a week with no neurological symptoms or signs. On follow-up at 4 months, the patient remains asymptomatic.

Discussion

Acute subdural hematomas of the posterior fossa are very rare lesions and account for between 0.3 % and 0.8% of all SDHs, and less than 10% of all posterior fossa traumatic lesions. ^[1] None of the 46 patients reported by d'Avella et al. had a RSDH. Hematomas in the retroclival region have been epidural hematomas in the pediatric population. ^[4],[5] RSDH is extremely rare , with only two previous cases being reported in literature. ^[2],[3]

All four cases, including the two in this report, have been male patients [Table - 1]. Three patients have been in their late teens, and one patient was aged four years. There probably is a predilection for this type of injury in patients less than 20 years of age. RSDH is classically seen on the CT scan as a convexo-concave hyperdense lesion lying behind the clivus and anterior to the brainstem. A thin SDH, restlessness in patients and older-generation CT scanners may be the reasons why these lesions have not been reported more frequently.

The mechanism of formation of RSDH is not clear. Supratentorial SDHs are caused by the tearing of bridging veins or the injury to cortical vessels and are very often associated with parenchymal injury. The reported cases of RSDH seem to be similar to those in group 1 in the report by d'Avella et al. ; as none had evidence of brainstem or cerebellar injury on the MRI, and all had a good GCS score and outcome. ^[1] Bridging veins seem to be the most probable cause of RSDH. The petrosal group and some of the minor veins near the foramen magnum appear to be most likely associated with this injury. ^[6] We do not subscribe to the view of Casey et al. that injury to bone or ligamentous structures at the craniovertebral junction could be a cause of SDH. ^[2] Any such injury would produce an epidural hematoma and not contribute to the formation of a subdural hematoma. It has been shown that cranial subdural blood can redistribute to the spinal subdural space. ^[3] It is our opinion that the presence of blood in the spinal subdural space in patients with RSDH is in itself not significant, with regard to patient management or prognosis.

The management of RSDH is dependent on the clinical condition of the patient. The presence of blood anterior to the brainstem warrants admission to an intensive care setting to pick up neurological deterioration early, as in one of our patients who needed surgery. A far lateral approach was adopted, as we would have done for a meningioma in this location. As the hematoma enveloped the vertebral and basilar arteries and their branches, as well as the sixth nerves, we were careful not to apply traction on the clot. We stopped at clot removal once we were sure of brainstem decompression, to prevent injury to vessels or nerves. Noncritical volumes of the SDH with a rapid redistribution of the hematoma into the spinal subdural space probably ensured that the patients treated conservatively did not develop neurological symptoms.

In conclusion RSDH is a very rare entity, seen in patients less than 20 years of age. Physicians need to be aware of this entity as the patients present with a good GCS score and except for the CT findings may not, in many centers, warrant admission. A careful watch must be kept on these patients as delayed deterioration is possible needing emergency surgery. The outcome and prognosis of these patients are good, probably due to redistribution of smaller hematoma volumes.

References

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