Spontaneous retroclival subdural hematoma associated with an
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Case Summary
A 72-year-old female with a past history of a right frontoparietal stroke and residual left hemiparesis presented to the ER with a one-day history of headache and confusion. One month previously she had been diagnosed with a deep venous thrombosis in her leg and had been started on lovenox and Coumadin. There was no reported history of antecedent trauma. Physical exam, other than the residual deficits from her previous infarct, was noncontributory. Laboratory values were within normal limits given patient’s current anticoagulation status. A noncontrast head CT was subsequently performed and demonstrated an area of extra-axial hyperdensity marginating the clivus and extending from the most inferiorly visualized aspect of the anterior foramen magnum cephalad towards the left and right cerebellopontine angle cisterns. A spontaneous retroclival subdural hematoma was suspected. Less likely considerations included an extra-axial hypercellular mass such as meningioma, lymphoma or plasmacytoma.

Imaging Findings
A CT angiogram of the head and neck was performed next to exclude any regional vascular anomalies, such as an occult arteriovenous malformation or dissection, as well as to assess for any abnormal regional enhancement. There was no evidence of an underlying enhancing mass or regional aberrant vessels. Elevation and dorsal displacement of the distal V4 vertebral artery segments and the basilar artery was observed. Anticoagulation was reversed in the ER with fresh frozen plasma and vitamin K was begun; the patient was subsequently admitted for supportive care and observation. At that time, an MRI of the brain and cervical spine, ordered to ensure a bland nature of the hemorrhage and to completely exclude any underlying mass, demonstrated the hematoma to have predominantly low signal on T2 FSE images and high signal on T1, consistent with intracellular methemoglobin. There was dissection from the superior aspect of the clivus distally through the anterior foramen magnum into the ventral spinal canal.