Objective:

This study aims to describe the clinical histories of patients who initially underwent CM1 decompression but were later diagnosed with a spinal CSF leak, highlighting delays in appropriate treatment due to misdiagnosis.

Background:

Chiari malformation type I (CM1) and spontaneous intracranial hypotension (SIH) can both present with headaches and low-lying cerebellar tonsils on imaging. The treatment, however, is dramatically different with CM1 patients undergoing suboccipital decompression and SIH patients receiving treatment for a spinal CSF leak. 

Design/Methods:

We present 7 individuals with inferior tonsillar descent who underwent Chiari posterior decompression and subsequently were found to have a spinal CSF leak. We detail the clinical presentations before and after Chiari decompression, imaging findings suggestive of CSF leak, and management strategies for CSF leak treatment and outcomes. 

Results:

All patients reported an orthostatic component to their headache. Retrospective MRI review demonstrated brain sag in all patients prior to decompression surgery. Post-operatively, five patients noted partial symptom improvement, and two had no benefit. All patients experienced persistent or recurrent headaches after surgery and were ultimately found to have a spinal CSF leak on myelography, for which they underwent targeted treatment. All patients improved after leak treatment; however, six developed rebound intracranial hypertension (RIH), managed with acetazolamide, with four requiring prolonged therapy.

Conclusions:

Low-lying cerebellar tonsils on brain MRI are a shared radiologic feature of both CM1 and SIH; however, all patients in our series demonstrated evidence of brain sag on preoperative MRI, a finding that is often overlooked. While transient symptom improvement may occur after decompression, recurrence of symptoms should prompt evaluation for an underlying CSF leak. Furthermore, the frequent occurrence of RIH after leak closure suggests that some patients may have had pre-existing susceptibility or history of idiopathic intracranial hypertension.