Idiopathic intracranial hypertension

• Idiopathic intracranial hypertension (IIH), sometimes called by the older names benign intracranial hypertension (BIH) or pseudotumor cerebri (PTC),

• characterized by an increased intracranial pressure in the absence of a tumor or other diseases.

• The main symptoms are headache, nausea and vomiting as well as pulsatile tinnitus , double vision and visual symptoms. If untreated, it may lead to vision loss due to associated swelling of the optic disc in the eye.

Pathophysiology

• The cause of IIH is not known. • The Monro-Kellie rule states that the intracranial pressure is determined by the

amount of brain tissue, cerebrospinal fluid (CSF) and blood inside the bony vault. Three theories therefore exist as to why the pressure might be raised in IIH: an excess of CSF production, increased volume of blood or brain tissue, or obstruction of the veins that drain blood from the brain .

• The first theory, that of increased production of cerebrospinal fluid, was proposed in early descriptions of the disease.

• A second theory posits that either increased blood flow to the brain or increase in the brain tissue itself may result in the raised pressure. Little evidence has accumulated , but both biopsy samples and various types of brain scans have shown an increased water content of the brain tissue.

• A third theory suggests that blood flow from the brain may be impaired or congested. Only in a small proportion of patients has underlying narrowing of the cerebral sinuses or veins been demonstrated. Congestion of venous blood may result from a generally increased venous pressure, which has been linked to obesity.

• occurs in women who are overweight.• The role of obesity in this disorder is unclear. • Obesity has been proposed to increase intra-abdominal

pressure, which, in turn, raises cardiac filling pressures. • This rise in pressure leads to impeded venous return

from the brain (due to the valveless venous system that exists from the brain to the heart) with a subsequent elevation in intracranial venous pressure.

• If not treated appropriately, chronic interruption of the axoplasmic flow of the optic nerves with ensuing papilledema due to this pressure may lead to irreversible optic neuropathy.

Epidemiology• 1 per 100,000 people, • can occur in children and adults.• The median age at diagnosis is 30.• IIH occurs predominantly in women, especially in the ages 20–45, who are

four to eight times more likely than men to be affected. • Overweight and obesity strongly predispose a person to IIH: women who are

more than ten percent over their ideal body weight are thirteen times more likely to develop IIH, and this figure goes up to nineteen times in women who are more than twenty percent over their ideal body weight.

• In men this relationship also exists, but the increase is only fivefold in those over 20% above their ideal body weight.

• Despite several reports of IIH in families, there is no known genetic cause for IIH. People from all ethnicities may develop IIH.

• In children, there is no difference in incidence between males and females.

Causes

• Most cases of idiopathic intracranial hypertension occur in young women who are obese and, less frequently, in men who are otherwise healthy. Patients with higher body mass indexes and recent weight gain are at an increased risk for this disorder.

• If this disorder presents in an individual who is not overweight, ruling out associated risk factors is necessary. These risk factors include systemic diseases , disruption of cerebral venous flow, certain endocrine or metabolic disorders, and exposure to or withdrawal from certain exogenous substances.

Exogenous substances • amiodarone,• antibiotics (eg, nalidixic acid, penicillin, tetracycline),• carbidopa, levodopa, • corticosteroids (eg, topical, systemic), • cyclosporine, • danazol, growth hormone,• indomethacin, ketoprofen, • lead,• leuprolide acetate, levonorgestrel implants, • lithium, • oral contraceptives, oxytocin, • phenytoin, • vitamin A (>100,000 U/d)/retinoic acid• withdrawal from corticosteroids

Systemic diseases

• A myriad of illnesses are associated with idiopathic intracranial hypertension. Some of these disorders result in an increased viscosity of the cerebrospinal fluid.

• anemia, • chronic respiratory insufficiency, • familial Mediterranean fever, • hypertension, • multiple sclerosis, • polyangiitis overlap syndrome, • psittacosis,• renal disease, • Reye syndrome,• sarcoidosis, • systemic lupus erythematosus, • thrombocytopenic purpura.

Disorders of cerebral venous drainage

• Cerebral venous compression by extravascular tumors or secondary thrombosis results in impaired absorption of the cerebrospinal fluid and, thus, idiopathic intracranial hypertension. Restriction of venous drainage from the head may be impaired with radical neck dissection, even if completed only on the right side (predominant drainage from the head is via the right jugular vein). Spontaneous recanalization usually occurs, but, if delayed, chronic papilledema may result.

• The diagnosis of cerebral sinus thrombosis may be missed with the exclusive use of computed tomography (CT). Therefore, either in patients who present atypically or in management dilemmas, ruling out cerebral venous thrombosis with the use of magnetic resonance imaging (MRI)/venography is worthwhile

– Endocrine disturbances: Pregnancy is occasionally associated with idiopathic intracranial hypertension. This disorder can present at any stage of pregnancy. Given the limitations of neuroimaging studies and of medically treating patients who are pregnant, both the diagnosis and the management of these patients are determined on a case-by-case basis. Any neuroimaging studies or therapeutics should be performed in conjunction with the patient's obstetrician.

CLINICALHistory

• Patients usually present with symptoms related to increased intracranial pressure. These symptoms include headache, transient visual obscurations, and diplopia due to unilateral or bilateral sixth nerve palsy. Rarely, patients presenting with increased intracranial pressure with related optic nerve edema may be asymptomatic.

• Nonspecific symptoms may include dizziness, nausea, vomiting, and tinnitus. • Headaches

– Headaches are recorded in 99% of patients presenting to neurologists and slightly less in patients presenting to ophthalmologists.

– The pain is generally described as being diffuse, which worsens in the morning and is exacerbated by the Valsalva maneuver.

• Transient visual obscurations: This visual symptom occurs in most patients. The disturbance usually lasts 1-5 seconds and is described as a graying out of vision. Orthostatic changes, such as standing up or bending over, induce this symptom.

• Diplopia: Patients who present with double vision most frequently complain of horizontal displacement of the images. Vertical diplopia is rare, but it has been reported.

Physical examination

• bilateral disc edema • This papilledema varies from patient to patient and is indistinguishable from optic nerve swelling caused by

intracranial space-occupying lesions. In more pronounced cases of disc swelling, macular involvement with subsequent edema and diminished central vision may be present.

• High-grade and atrophic papilledema in addition to subretinal hemorrhages are poor visual prognostic signs.

• In some instances, the disc swelling is asymmetric, or, rarely, the appearance of the optic nerve may be relatively normal.

• If left untreated, chronic disc swelling eventually leads to clinically significant visual loss. Although all patients present with enlarged blind spots during their initial perimetry, uncontrolled papilledema results in progressive peripheral visual field constriction or nerve fiber bundle defects (eg, nasal depression, nasal steps, arcuate scotomas).

• The central visual field is affected in end-stage chronic papilledema. • Sudden loss of central vision may result from an associated anterior ischemic optic neuropathy, a vascular

occlusion, or an associated subretinal neovascular membrane. • The diplopia noted in patients with idiopathic intracranial hypertension is invariably due to unilateral or

bilateral sixth nerve palsy. These cranial nerve palsies diminish with the lowering of the intracranial pressure.

• Occasionally, patients with diplopia present with oculomotor or trochlear nerve palsy. • In rare instances, vertical diplopia is due to a skew deviation

• papilledema

FUNDOSCOPIC EXAM

Normal Papilledema

DIFFERENTIALSPapilledema

• intracranial tumour• dural sinus thrombosis• Pseudopapilledema • Drusen of the optic nerve heads • Malignant hypertension • Bilateral infiltrative/infectious/inflammatory optic

neuropathy • Bilateral anterior ischemic optic neuropathy • Bilateral optic nerve papillitis • Bilateral optic nerve tumors ,eg, glioma, meningioma

Diagnosis

The original criteria for IIH were described by Dandy in 1937.

• Dandy criteria1. Signs & symptoms of increased ICP – CSF pressure >25

cmH2O

2 .No localizing signs with the exception of abducens nerve palsy

3 .Normal CSF composition4 .Normal to small (slit) ventricles on imaging with no

intracranial mass

Modified Dandy criteria1. Symptoms of raised intracranial pressure (headache,

nausea, vomiting, transient visual obscurations, or papilledema)

2 .No localizing signs with the exception of abducens (sixth) nerve palsy

3. The patient is awake and alert4. Normal CT/MRI findings without evidence of thrombosis5 .LP opening pressure of >25 cmH2O and normal biochemical

and cytological composition of CSF6 .No other explanation for the raised intracranial pressure

Neuroimaging

– A patient with bilateral disc swelling should undergo urgent neuroimaging studies to rule out an intracranial mass or a dural sinus thrombosis.

– Although CT is certainly adequate in most instances, MRI and magnetic resonance venography are effective in ruling out both a mass lesion and a potential dural sinus thrombosis.

• In the setting of idiopathic intracranial hypertension, the findings on neuroimaging studies either are normal or demonstrate small slitlike ventricles, enlarged optic nerve sheaths, and occasionally an empty sella

Ultrasonography

– Standardized A-scan orbital ultrasonography precisely measures the diameter of the optic nerve sheath.

– If this diameter increases in primary gaze and diminishes by 25% in eccentric gaze (30° test), then increased subarachnoid fluid surrounding the optic nerve is presumably present. This finding is consistent with papilledema if it is bilateral.

• The drawback of this noninvasive technique is that it requires a highly skilled clinician to obtain reproducible results

Lumbar puncture

– Once an intracranial mass lesion is ruled out, a lumbar puncture is indicated. The opening pressure should be measured with the patient relaxed to avoid a falsely elevated pressure reading.

– The clinician performing the procedure must indicate to the ophthalmologist if any specific difficulty was encountered that may have falsely elevated the pressure reading.

– Unfortunately, some patients demonstrate a transiently normal pressure despite their harboring idiopathic intracranial hypertension. Confirming the disease in these patients is difficult.

• Besides the value of the opening pressure, the clarity and the color of the cerebrospinal fluid should be noted. In addition, the cerebrospinal fluid should be forwarded for assessment of the cell count, cytology, culture, glucose, protein, and electrolyte concentration. All of these findings are normal in patients with idiopathic intracranial hypertension

The medical management

– Weight control for patients who are overweight • Most patients with this disorder are females who are overweight. Weight

loss is a cornerstone in the management of these patients. Unfortunately, weight reduction generally proves to be a difficult task for these patients.

• As little as a 6% weight loss has been demonstrated to result in a reduction of the intracranial pressure with the accompanying resolution of papilledema.

• To formalize the process of weight reduction, referral to a dietitian may be appropriate– Treatment of related underlying diseases – Cessation of exogenous agents related to increased intracranial

pressure

DRUGS

• Acetazolamide appears to be the most effective diuretic in lowering the intracranial pressure.

• The initial dose should be 1 g/d. Although for compliance purposes, the 500 mg sequel taken orally twice a day is preferred;

• This dose can be increased to 2 g/d, although most patients do not tolerate the troubling adverse effects (eg, extremity paresthesias, fatigue, metallic taste when drinking carbonated beverages, decreased libido) of this medication at this high dose.

• In the event of intolerance to acetazolamide, furosemide may be used as a replacement diuretic in this group. Unfortunately, furosemide does not appear to be as effective as acetazolamide

• Drug Name Acetazolamide (Diamox, Diamox Sequels)• Description Nonbacteriostatic sulfonamide; potent CA inhibitor, which is effective in diminishing fluid secretion. Lowers intracranial

pressure by decreasing production of cerebrospinal fluid. Inhibition of CA results in a drop in sodium ion transport across the choroidal epithelium. Reduction of cerebrospinal fluid production occurs within hours.

• Adult Dose 500 mg sequels PO bid; up to 2,000 mg PO bid

Alternatively, 250 mg tab PO qid• Pediatric Dose 5-10 mg/kg PO qid• Contraindications Documented hypersensitivity; hepatic disease; severe renal disease; adrenocortical insufficiency; severe pulmonary

obstruction• Interactions Can decrease therapeutic levels of lithium and alter excretion of drugs (eg, amphetamines, quinidine, phenobarbital,

salicylates) by alkalinizing urine• Pregnancy C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to

fetus• Precautions Caution in severe pulmonary disease or in those patients taking high doses of aspirin; adverse reactions may include

drowsiness, paresthesias, anaphylaxis, Steven-Johnson syndrome, rash, crystalluria, renal calculus (patients are advised to drink sufficient amounts of water during the day), bone marrow depression, thrombocytopenic purpura, hemolytic anemia, leukopenia, pancytopenia, and agranulocytosis

DRUGS• Drug Name Furosemide (Lasix)• Description Unclear how it inhibits cerebrospinal fluid production. A combination of CA inhibition and effect on sodium absorption across

the choroid plexus may result in the decrease of cerebrospinal fluid production.• Adult Dose 20-40 mg PO bid initially; may increase by 20 mg to maximum 80 mg PO bid with appropriate monitoring• Pediatric Dose Not established• Contraindications Documented hypersensitivity; hepatic coma; anuria; severe electrolyte depletion• Interactions Metformin decreases furosemide concentrations; furosemide interferes with hypoglycemic effect of antidiabetic agents and

antagonizes muscle relaxing effect of tubocurarine; auditory toxicity appears to be increased with coadministration of aminoglycosides and furosemide; hearing loss of varying degrees may occur; anticoagulant activity of warfarin may be enhanced when taken concurrently with this medication; increased plasma lithium levels and toxicity are possible when taken concurrently with this medication

• Pregnancy C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to

fetus• Precautions Perform frequent serum electrolyte, carbon dioxide, glucose, creatinine, uric acid, calcium, and BUN determinations during first

few months of therapy and periodically thereafter

– Corticosteroids

• Corticosteroids are effective in lowering the intracranial pressure in those patients with an inflammatory etiology for their idiopathic intracranial hypertension. • In addition, steroids may be used as a supplement to

acetazolamide to hasten recovery in patients who present with severe papilledema.

Surgical Care

• Optic nerve sheath fenestration – Optic nerve sheath fenestration has been demonstrated to result in the reversal of

optic nerve edema with some recovery of optic nerve function. The approach to the optic nerve may be from the medial or lateral aspect of the orbit; each technique has its benefits and drawbacks.

– Occasionally, a bilateral curative effect of the papilledema occurs from unilateral surgery. However, if this is not the case, then the opposite nerve must undergo the same procedure.

– Although the intracranial pressure remains elevated in these patients postoperatively, the local filtering effect of the fenestration acts as a safety valve and eliminates the pressure from being transmitted to the optic nerve.

– Complications related to this procedure include diplopia, optic nerve injury, vascular occlusion, a tonic pupil, and the inherent risk of hemorrhage and infection with intraconal surgery.

• Unfortunately, Spoor has demonstrated that the long-term success rate of this operation may be only 16%.

Optic nerve sheath fenestration

• Via lateral orbitotomy app

•Window of dura and arachnoid made

•Arachnoid excised

•CSF allowed to drain

Cerebrospinal fluid diversion procedures

• lumboperitoneal shunt,• ventriculoperitoneal shunt– who do not respond to maximum medical

treatment. – patients with intractable headaches, where no

access is available to a surgeon who is comfortable with optic nerve sheath fenestration

– patients with a failed optic nerve sheath fenestration.

LP,VP SHUNTS• The initial procedure is usually a lumboperitoneal (LP) shunt, which

connects the subarachnoid space in the lumbar spine with the peritoneal cavity. Generally, a pressure valve is included in the circuit to avoid excessive drainage when the patient is erect and therefore has a relatively high ICP. LP shunting provides long-term relief in about half the cases; others require revision of the shunt, often on more than one occasion—usually due to shunt obstruction.

• If the lumboperitoneal shunt needs repeated revisions, a ventriculoatrial or ventriculoperitoneal shunt may be considered. These shunts are inserted in one of the lateral ventricles of the brain, usually by stereotactic surgery, and then connected either to the right atrium of the heart or the peritoneal cavity, respectively. Given the reduced need for revisions in ventricular shunts, it is possible that this procedure will become the first-line type of shunt treatment.

• Poor Prognostication Factors– Older age– Raised IOP– Systemic hypertension – DM– Weight gain during first year prior to diagnosis– Anaemia– High myope