Ear Center: Benign Intracranial Hypertension
Intracranial hypertension (IH) is a disorder that is in the differential diagnosis of individuals who suffer from chronic daily headache. IH may be idiopathic (without a defined cause) or symptomatic of clotted intracranial veins (venous sinus occlusion), various drug side effects, or radical neck dissection performed for cancer treatment.
Idiopathic IH (also called pseudotumor cerebri because the pituitary gland, flattened by the increased intracranial pressure, appears to be absent from its fossa) is predominantly seen in young adult women who are obese. Such individuals usually present with complaints of persistent headache, often with migrainous features. In a minority of individuals with IH, headaches may not even occur. Other symptoms of IH include transient visual obscurations which are very brief episodes of visual clouding involving one or both eyes, pulsatile ear ringing (pulsatile tinnitus), double vision (diplopia) related to sixth cranial nerve weakness (paresis), and rarely even frank visual loss secondary to ongoing vision nerve (optic nerve) involvement. Rare reports of neck pain (cervical radicular pain) have been noted which is presumably secondary to nerve root dilatation due to the effects of increased cerebrospinal fluid (CSF) pressure (fluid surrounding the brain).
Physical examination usually reveals evidence of vision nerve pressure (papilledema) and occasionally a sixth cranial nerve palsy. Cases of IH have been noted without papilledema. The reason for the lack of papilledema in some patients may be secondary to vision nerve (optic nerve) sheath defects or perhaps early intracranial hypertension occurring prior to the development of papilledema.
As various space occupying lesions in the brain may produce increase in intracranial pressure and papilledema on examination, it is paramount to proceed with neuro-imaging studies to exclude other disorders. In idiopathic IH, a brain magnetic resonance imaging (MRI) study is usually unrevealing although an empty sella turcica (pituitary gland fossa) may be noted. However, the latter may also be seen in normal individuals who do not have IH.
The pathophysiology (underlying cause) of idiopathic IH in not definitely known. Potential mechanisms include: (1) increased production of CSF, (2) an increase in intracranial venous pressure, (3) a decreased rate of CSF absorption, or (4) an increase in brain interstitial fluid (fluid within the brain substance itself). Some studies in individuals with IH have shown evidence of increased pressure in the cerebral venous sinuses with some evidence of venous outflow obstruction related to possible mural thrombosis (clots along the walls of veins) or venous stenosis (narrowing). In addition, some studies have shown individuals with elevation of right atrial pressure (upper chamber of the right side of the heart) although not necessarily with evidence of right heart failure. Based on these studies, it is recommended that patients suspected on having IH due to non-space occupying lesions undergo magnetic resonance venography (MRV) to further assess the venous sinuses.
If left untreated, idiopathic IH may lead to visual dysfunction with studies showing at least thirty percent (30%) of patients experiencing visual difficulties including enlargement of the blind spot and other visual field deficits. Visual acuity diminution may eventually occur.
The treatment of idiopathic intracranial hypertension involves modalities to lower the CSF pressure. These can include:
- agents such as the carbonic anhydrase inhibitors (acetazolamide or Diamox®)
- diuretics (water pills) such as furosemide (Lasix®)
- serial lumbar punctures (spinal taps)
- various surgical procedures including shunting procedures and optic nerve (vision nerve) fenestration
If you would like to learn more about idiopathic intracranial hypertension, please call our office at (336) 273-9932.
Edited from Lewitt E. Idiopathic Intracranial Hypertension. April Newsletter, Lewitt Headache & Neck Pain Clinic, PLLC, Greensboro, NC