= Idiopathic Intracranial Hypertension (= Benign Intracranial Hypertension = BIH = pseudotumor cerebri)
- sy of raised ICP
- headache (up to 99%, diffuse, worse a.m., exacerbated by Valsalva)
- transient visual obscurations (most patients, 1-5secs, 'greying out' of vision, induced by { standing up | bending over }
- diplopia: usu due to uni/bilat 6th nerve (abducens) palsy: horizontal image displacement; (rarely vertical displacement: eg 3rd (oculomotor) or 4th nerve (trochlear) palsy)
- nonspecific:
- rarely:
- sx of raised ICP
- bilat papilloedema (rarely: asymmetric or unilat)
- visual loss: enlarged blind spot (100%), progressive peripheral VF constriction / nerve fibre bundle defects, central VF affected only in end-stage chron papilloedema
- sudden loss of central vision: if associated ant isch optic neuropathy, vascular occlusion, or subretinal neovascular membrane
- 6th nerve (abducens) palsy
- normal neuroimaging (except nonspecific findings of raised ICP)
- icrd CSF pressure (>25cm H2O [pubmed: 95% nml=10-25]) with nml composition
Risk factors:
- mostly: obese young women (although role of obesity unclear)
- exogenous substances: drugs [NB: also withdrawal from corticosteroids]
- systemic disease (eg with icrd blood viscosity), anaemia, chron respir insuff, familial Mediterranean fever, hypertension, MS, renal disease, sarcoidosis, SLE, ITP
- disorders of cerebral venous drainage: eg cerebral venous compression by extravascular tumours or secondary thrombosis, post radical neck dissection (esp on right), cerebral sinus thrombosis
- endocrine causes: pregnancy
Differential diagnosis
- Pseudopapilloedema
- Drusen of the optic nerve heads
- malignant hypertension
- bilat infiltrative/infectious/inflammatory optic neuropathy
- bilat ant isch optic neuropathy
- bilat optiv nerve papillitis
- bilat optic nerve tumours (eg glioma, meningioma)
Investigations
- Imaging
- urgent { CT | MRI+MR venography: r/o dural sinus thrombosis }: usu nml or small slitlike ventricles, enlarged optic nerve sheaths, occasionally empty sella
- [ orbital US to measure optic nerve sheath diameter ]
- Lumbar puncture: opening pressure (patient relaxed): NB can be transiently nml; [CSF: nml composition!]
Treatment
- monitor optic nerve fx
- weight control if icrd BMI (as little as 6% can resolve papilloedema)
- Tx underlying diseases
- eliminate exogenous causative agents
- Diuretics: Acetazolamide (Diamox): carboanhydrase inhibitor, lowers CSF production: { 500mg bd | 250mg qds } PO [-> 2g/d idd, although often limited by SE: paraestehesia, fatigue, metallic taste, dcrd libido]; alternatively: Furosemide (although less effective)
- Corticosteroids: initially in addition to diuretics if severe papilloedema; if underlying inflammatory disease, but short-term use only
- Surgical Tx if medical Tx ineffective (worsening visual fx):
- optic nerve sheath fenestration: sometimes unilat, often bilat; long-term success only 16% ?
- CSF diversion procedure: { lumboperitoneal | ventriculoperitoneal } shunt
if untreated: risk of irreversible optic neuropathy (VF constriction, loss of colour vision)
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