Abducens nerve palsy as a false localising sign in spontaneous intracranial hypotension

Spontaneous intracranial hypotension (SIH) with the formation of a spinal longitudinal epidural collection (SLEC) is an important treatable cause of headache. Left untreated, neurological sequelae can include cranial neuropathy, superficial siderosis and brain-sagging dementia. We describe a male in his late 40s presenting with orthostatic low-pressure headache and binocular horizontal diplopia due to an isolated left abducens nerve palsy, a recognised false localising sign. Imaging revealed intracranial hypotension associated with a SLEC, attributed to a cervical osteophyte associated dural tear. An empirical lumbar epidural blood patching led to rapid clinical improvement and radiological resolution of the SLEC on follow-up imaging. This case highlights that abducens nerve palsy, traditionally considered a false localising sign of raised intracranial pressure, can occur in low-pressure states. Spinal imaging is crucial for identifying SLEC and guiding management, enabling prompt treatment to prevent severe neurological outcomes. We also review the causes, diagnosis and management of SIH.