52-year-old female with vertigo, headache, tinnitus, eye twitching, and general instability while walking. Unsuccessfully treated with Epley maneuver, benzodiazepine medications.
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Diagnosis: Idiopathic intracranial hypertension (IIH)
MRI images demonstrate a partially empty sella turcica, increased fluid in the optic nerve sheaths, increased tortuosity of the bilateral optic nerves, narrowing of the transverse sinuses, dehiscence of the right tegmen tympani with inferior protrusion of brain parenchyma (meningoencephalocele) and low-lying cerebellar tonsils protruding into the foramen magnum with a pointed appearance, compatible with/mimicking Chiari I malformation.
Idiopathic intracranial hypertension (IIH), also known as pseudotumor cerebri, is an increase in intracranial pressure without identifiable cause. The most common demographic group affected is obese, middle-aged women, who typically present with symptoms including headache, papilledema, visual disturbances, and pulsatile tinnitus. Lumbar puncture may reveal normal CSF composition with elevated opening pressures.
The etiology of IIH is poorly understood, but the most commonly proposed mechanisms include those related to increased CSF production, decreased CSF absorption, increased cerebral arterial pressure, and increased venous blood volume. Several conditions are associated with IIH, including chronic kidney disease, systemic lupus erythematosus (SLE), high-dose vitamin A intake, long-term tetracycline antibiotic, and hormonal contraceptive use.
Diagnosis of IIH relies mainly on imaging and clinical features, including the modified Dandy criteria: symptoms of raised intracranial pressure, normal CT/MRI findings without evidence of thrombosis, lumbar puncture opening pressure >25 cmH2O with normal CSF composition, and no other explanation for the raised intracranial pressure.
Once alternative causes for intracranial hypertension have been excluded, imaging can be used to make the diagnosis of IIH. MR imaging findings that support a diagnosis of IIH include a partially empty sella turcica, small ventricles, enlarged and tortuous optic nerve sheaths, protrusion of the optic nerve papilla into the posterior globes, meningoceles or meningoencephaloceles typically in the temporal bone or sphenoid wing and cerebellar tonsillar ectopia, which may mimic Chiari I malformation. CT imaging is typically normal, but may show slit-like ventricles, empty sella, and enlarged optic nerve sheaths.
Treatment methods include weight loss, carbonic anhydrase inhibitors (acetazolamide), therapeutic lumbar puncture (no LP was performed for our patient due to prominent low lying cerebellar tonsils), and surgical interventions (lumboperitoneal shunting, optic nerve fenestration).
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