Sinking brain syndrome: Craniotomy can precipitate brainstem herniation in CSF hypovolemia

Intracranial hypotension associated with CSF hypovolemia can occur spontaneously from cryptic CSF leaks, after trauma, or from iatrogenic causes, especially lumbar puncture. It is not widely known that it increases the risk of complications from craniotomy. We present two cases in which patients with CSF hypovolemia experienced posture-dependent deteriorations in level of consciousness after craniotomy. ### Patient 1. A 59-year-old woman sought treatment for progressive headache. CT and MRI demonstrated bilateral subdural fluid collections with diffuse pachymeningeal enhancement and a left subdural hematoma with mild left to right shift. She had a craniotomy with evacuation of the hematoma and dural biopsy. This showed only thrombus and normal dura. Headache persisted postoperatively, and she became progressively more obtunded despite head elevation. CT showed bifrontal pneumocephalus and effacement of the suprasellar cistern. By postoperative day 5, she was responsive only to pain and had no voluntary eye movements. Pupils were reactive at 4 mm, but plantar responses were extensor. Neurology was consulted. Further history disclosed the preoperative headaches were orthostatic. Reanalysis of the radiologic …