The most common neurological symptom of spontaneous intracranial hypotension (SIH) is abducens nerve paresis, and the precise pathophysiology is unclear. The accepted explanation is traction on the cranial nerves caused by the downward displacement of the cranial content. We herein report magnetic resonance imaging of SIH that can explain the mechanism underlying abducens nerve paresis. The cavernous sinuses were particularly thickened compared with the surrounding dura. This phenomenon can be explained by venous swelling, which can occur after leakage of cerebrospinal fluid in a closed cavity. This swelling pushes the abducens nerve up, which then causes abducens nerve paresis.
Keywords: abducens nerve paresis; cavernous sinus; digital subtraction angiography; hypertrophic pachymeningitis; spontaneous intracranial hypotension.