To broaden the differential diagnosis of non-traumatic, non-aneurysmal subarachnoid hemorrhage (SAH) to include leptomeningeal metastatic malignancy.

Ruptured cerebral aneurysms are common etiologies of non-traumatic SAH. To the best of our knowledge, there is no published information describing non-traumatic subarachnoid hemorrhage as the possible presenting clinical sign of metastatic malignancy.

In this case report, we describe the clinical course of a 43-year-old male who presented to the emergency room with a thunderclap headache. Neurological examination was normal. Initial CT was negative for hemorrhage. Cerebrospinal fluid analysis revealed pleocytosis (TNC 84), RBCs (30,000) with xanthochromia, total protein (492), and significant hypoglycorrhacia (glucose 26). MRI brain revealed sulcal SAH. There was no pathological contrast enhancement. Formal cerebral angiogram revealed no underlying vascular abnormalities. The patient’s headaches improved, and he was discharged home with close outpatient follow up.

Over the subsequent months, he developed subacute paraparesis. Repeat MRI brain without contrast was unchanged.  Upon follow-up, his neurological exam was suggestive of spinal cord pathology. He underwent emergent complete spine imaging that revealed leptomeningeal metastatic disease. One week prior, he underwent a foot lesion biopsy that revealed melanoma. Cytology from repeat CSF analysis was also consistent with metastatic melanoma. He was admitted for initiation of disease-directed chemotherapy and corticosteroids. 

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We suspect the patient’s initial presentation of thunderclap headache and SAH represented an early, radiologically occult phase of his metastatic melanoma. In patients with non-aneurysmal SAH who have a negative four-vessel cerebral angiogram, imaging of the spine should be considered. Metastatic malignancy should be included in the differential of non-traumatic and non-aneurysmal SAH, particularly in patients with a known history of cancer or those of otherwise high risk, to allow for early detection and expedited disease-directed treatment.