What is the definition of idiopathic intracranial hypertension (IHH)?
Idiopathic intracranial hypertension is a condition that causes increase intracranial pressure, with no identifiable cause, such as a mass lesion or hydrocephalus.
What is the classic clinical presentation of idiopathic intracranial hypertension?
The classic clinical presentation may include frontal/retro-ocular headaches of fluctuating intensity, tinnitus, dizziness, nausea, vomiting, transient visual impairment, diplopia due to cranial nerve VI palsy, neck pain, back pain, radicular pain, cognitive disturbances, bilateral and occasionally unilateral papilledema. Visual loss is the most feared sequela of IIH. The disease is prevalent in obese young women, older men with sleep apnea, and patients with endocrine conditions. It is also associated with the use of several medications, primarily vitamin A and the tetracycline antibiotics.
How is the diagnosis of idiopathic intracranial hypertension confirmed?
The diagnosis of IIH is established by the modified Dandy Criteria, which basically refers to an elevated opening pressure at lumbar puncture >25 cm CSF in adults and >28 cm CSF in children, with no definable aetiology and normal CSF composition. This condition may be suspected clinically, which consists of papilledema or other signs and symptoms related to an increased intracranial pressure (ICP). Brain imaging is mandatory and usually shows findings that indicate IIH.
What is the pathophysiology of idiopathic intracranial hypertension?
The underlying pathophysiology of IHH is uncertain, but it seems that this condition likely represents a disorder of CSF regulation, potentially through excessive CSF production or reduced resorption, and venous outflow obstruction, which results in raised intracranial pressure.
What are the imaging findings in idiopathic intracranial hypertension?
The imaging findings may include: intraocular protrusion of optic nerve head (papilledema), restriction of diffusion with a bright spot at the optic nerve head, postcontrast enhancement and hyperintensity of the optic nerve head, on T1 or 3D-FLAIR, which is a sensitive and specific sign of papilledema in patients with IIH. Other signs are: flattening of the posterior optic globe, dilatation of the optic nerve sheaths, tortuosity of the optic nerves, empty sella or partially empty sella, and transverse sinus stenosis. The cerebellar tonsillar position may or may not be low-lying in IHH. The ventricles are usually normal or slightly small in size. CT or MR venography is mandatory and usually shows: stenosis of the dominant or both transverse sinuses, which is the most sensitive imaging indicator of IHH.
What is the aim of the treatment of idiopathic intracranial hypertension?
The main approaches to the treatment of IIH are reducing intracranial pressure, preserving vision, and relieving headaches. Medical interventions range from dietary therapy aiming for weight loss, through medications with acetazolamide or topiramate, and surgical treatment. If vision deteriorates despite treatment, CSF diversion procedures, as well as optic sheath fenestration, are considered. Serial lumbar punctures are an option in some patients. In selected patients, venous sinus stent placement may be useful to treat IHH.
The findings include a partially empty sella, with the pituitary gland flattened against the wall of the sella, slightly distension of optic nerve sheath complex bilaterally, without tortuous optic nerves, in conjunction with a focal posterior flattening of the globes at the insertion of the optic nerves. There is also a cerebellar tonsillar ectopia of 3.5 mm below the foramen magnum.
MR venography reveals focal stenosis of the lateral aspect of both transverse sinuses, more prominent on the right side, and excludes cerebral sinus thrombosis.
There is no evidence of hydrocephalus, mass, structural vascular lesion, and no abnormal meningeal enhancement.
These imaging patterns are consistent with the diagnosis of idiopathic intracranial hypertension (IIH).
The patient underwent a lumbar puncture, for CSF testing, which indicated an elevated opening pressure of 40 cm CSF, and normal CSF composition.