Overview
Definition:
Idiopathic Intracranial Hypertension (IIH), also known as pseudotumor cerebri, is a neurological disorder characterized by increased intracranial pressure (ICP) in the absence of a demonstrable intracranial mass lesion or hydrocephalus
In adolescents, it presents with a distinct set of challenges and management considerations.
Epidemiology:
IIH is more common in overweight or obese women of reproductive age
However, it can occur in children and adolescents of any sex, with a bimodal age distribution peaking in early childhood and adolescence
Adolescents, particularly females, are at increased risk, often associated with rapid weight gain or obesity.
Clinical Significance:
Untreated or inadequately managed IIH can lead to permanent visual impairment due to papilledema and optic nerve damage
Prompt diagnosis and appropriate treatment, including pharmacological management with acetazolamide, are crucial to preserve vision and alleviate symptoms, making it a critical topic for pediatricians and neurology residents.
Clinical Presentation
Symptoms:
Headache, often daily and diffuse, worse in the morning or with Valsalva maneuvers
Visual disturbances, including transient visual obscurations (TVOs), blurred vision, diplopia (especially in the VI nerve palsy pattern), and visual field defects
Pulsatile tinnitus (a rhythmic whooshing sound synchronous with the heartbeat)
Nausea and vomiting, especially with severe headaches.
Signs:
Papilledema (optic disc edema) on funduscopic examination is the hallmark sign, graded using the Frisen scale
Sixth cranial nerve palsy, leading to abducens nerve dysfunction and potential horizontal diplopia
Visual field deficits, often beginning with enlarged blind spots and progressing to arcuate and peripheral constriction
Normal neurological examination apart from cranial nerve findings and papilledema.
Diagnostic Criteria:
The modified Dandy criteria are commonly used: Elevated opening pressure (>25 cm H2O in adults, >20 cm H2O in children) on lumbar puncture
Normal cerebrospinal fluid (CSF) composition
No evidence of intracranial mass lesion or hydrocephalus on neuroimaging (MRI brain with venography is preferred)
Normal or near-normal neurological examination (apart from papilledema and VI nerve palsy)
Absence of other identifiable causes of elevated ICP.
Diagnostic Approach
History Taking:
Detailed history of headache characteristics (onset, frequency, severity, exacerbating/alleviating factors)
Assessment of visual symptoms: TVOs, blurring, diplopia, changes in peripheral vision
Inquiry about pulsatile tinnitus and its characteristics
Significant weight gain or history of recent rapid weight change
Review of medications, including oral contraceptives or vitamin A supplementation
Family history of IIH.
Physical Examination:
Thorough funduscopic examination to assess for papilledema and grade its severity
Cranial nerve examination, paying close attention to extraocular movements and pupillary responses
Visual acuity and visual field assessment (confrontation fields)
Neurological examination to rule out focal deficits
Measurement of weight and height for BMI calculation.
Investigations:
Lumbar puncture to measure opening pressure and obtain CSF for analysis (cell count, protein, glucose) to exclude secondary causes of ICP elevation
MRI brain with contrast to rule out mass lesions, hydrocephalus, or venous sinus thrombosis
MR venography (MRV) or digital subtraction angiography (DSA) to assess for dural venous sinus stenosis or thrombosis
Visual evoked potentials (VEPs) and optical coherence tomography (OCT) can provide objective measures of optic nerve function and structural changes.
Differential Diagnosis:
Intracranial mass lesions (tumors, abscesses)
Hydrocephalus
Dural venous sinus thrombosis
Meningitis or encephalitis
Cerebral venous malformations
Arachnoid cysts
Cerebral edema from metabolic or toxic causes
Complications of cranial irradiation
Chronic subdural hematoma.
Management
Initial Management:
Immediate stabilization and prompt diagnostic workup, including lumbar puncture and neuroimaging
If visual impairment is severe or progressing rapidly, surgical intervention may be considered urgently
Weight loss counseling and referral to a multidisciplinary weight management program is a cornerstone of long-term management.
Medical Management:
Acetazolamide is the first-line pharmacotherapy
It acts by inhibiting carbonic anhydrase in the choroid plexus, reducing CSF production
Initial dosage for adolescents is typically 10-15 mg/kg/day divided into 2-4 doses, with a maximum of 1000 mg/day
Doses may be titrated based on ICP response and symptom control
Side effects include paresthesias (especially in the extremities), metallic taste, anorexia, metabolic acidosis, and renal stones
Close monitoring for effectiveness and tolerability is essential
Other diuretics like furosemide may be considered as adjuncts in refractory cases or if acetazolamide is not tolerated, though less effective for CSF reduction
Topiramate can also be used due to its carbonic anhydrase inhibitory and GABAergic effects, but it may also cause metabolic acidosis and weight loss.
Surgical Management:
Surgical options are reserved for cases of progressive visual loss despite optimal medical therapy or in patients intolerant to medical management
Optic nerve sheath fenestration (ONSF) is the most common procedure, creating small slits in the optic nerve sheath to relieve pressure
Ventriculoperitoneal (VP) shunt or lumboperitoneal (LP) shunt placement can also be considered to divert excess CSF, though ONSF is generally preferred for preserving vision.
Supportive Care:
Regular ophthalmologic and neurological follow-up is critical to monitor visual acuity, visual fields, papilledema grade, and ICP
Patient education regarding the chronic nature of the condition, importance of adherence to treatment, and lifestyle modifications (weight management) is paramount
Pain management for headaches should be addressed appropriately.
Complications
Early Complications:
Rapid visual deterioration, including permanent vision loss and blindness
Worsening headaches and nausea/vomiting leading to dehydration and electrolyte imbalances
Papilledema progression.
Late Complications:
Chronic visual field defects
Optic atrophy
Persistent headaches
Recurrence of IIH after successful treatment, often associated with weight regain.
Prevention Strategies:
Aggressive weight management through diet and exercise
Adherence to prescribed medical therapy
Regular monitoring and timely adjustments of treatment
Avoiding medications that can exacerbate IIH (e.g., tetracyclines, vitamin A).
Prognosis
Factors Affecting Prognosis:
Early diagnosis and treatment
Degree of initial visual impairment
Patient adherence to treatment and weight loss
Presence of comorbidities
The most important factor for visual outcome is the severity of papilledema at diagnosis and the response to treatment
Patients who achieve significant weight loss generally have better long-term outcomes and lower rates of recurrence.
Outcomes:
With prompt and appropriate management, many patients experience improvement in headache and stabilization or improvement of visual function
However, some degree of permanent visual field deficit may persist in a significant proportion of individuals
Remission is possible, particularly with substantial weight loss, but recurrence is not uncommon.
Follow Up:
Lifelong follow-up is generally recommended, especially for individuals who remain overweight
Ophthalmologic assessments should be frequent initially (e.g., monthly) and then gradually spaced out (e.g., every 3-6 months) based on stability
Monitoring for ICP and symptoms should continue indefinitely
Regular assessment of weight and BMI is crucial.
Key Points
Exam Focus:
Remember the modified Dandy criteria for IIH diagnosis
Acetazolamide dosage (10-15 mg/kg/day, max 1000 mg/day) and common side effects (paresthesias, acidosis)
Indications for surgical management (progressive vision loss despite medical therapy)
The critical role of weight loss in management and prognosis.
Clinical Pearls:
Always perform a funduscopic exam in any adolescent presenting with chronic headaches or visual disturbances
The presence of pulsatile tinnitus should raise suspicion for IIH
MR venography is crucial to rule out dural venous sinus thrombosis, a treatable cause of secondary IIH
Papilledema grading (Frisen scale) helps stratify risk and monitor progression.
Common Mistakes:
Delaying lumbar puncture and neuroimaging due to concern for lumbar puncture headache, thus missing the diagnosis
Inadequate weight loss counseling or patient adherence to management strategies
Prescribing acetazolamide without adequate patient education on side effects and the need for regular follow-up
Failure to consider surgical options in cases of rapid visual deterioration.