Emergency Medicine Hub / Neurology & Psychiatry • 3 min read • 2 sections

Idiopathic Intracranial Hypertension & Normal Pressure Hydrocephalus

Comprehensive emergency evaluation and protocolized management of CSF hydrodynamic disorders: Idiopathic Intracranial Hypertension (IIH/Pseudotumor Cerebri; young obese females of childbearing age, pulsatile tinnitus, transient visual obscurations, horizontal diplopia/CN VI abducens palsy, papilledema, modified Dandy criteria, lumbar puncture opening pressure > 25 cmH2O, Acetazolamide, optic nerve sheath fenestration to prevent permanent blindness); and Normal Pressure Hydrocephalus (NPH; Hakim's classic triad: gait disturbance ['magnetic gait'], urinary incontinence, cognitive decline ['wobbly, wet, wacky'], ventriculomegaly disproportionate to sulcal enlargement on MRI, Evans index > 0.30, and high-volume diagnostic lumbar puncture tap test).

Resuscitation Quick Actions • First 2 Minutes

High-Acuity

IIH Opening Pressure

Lumbar puncture in lateral decubitus position: opening pressure > 25 cmH2O (or > 28 in children) confirms elevated pressure

MRI + MRV Mandate

Obtain MRI Brain + MR Venography (MRV) BEFORE lumbar puncture to exclude mass lesion, hydrocephalus, and cerebral venous sinus thrombosis

First-Line Medical IIH

Acetazolamide 500 to 1,000 mg PO BID (titrated up to 2–4 g/day); carbonic anhydrase inhibitor that reduces choroid plexus CSF production

CN VI Palsy (Abducens)

False localizing sign: impaired lateral gaze due to stretching of the long intracranial course of CN VI over the petrous temporal ridge

NPH Hakim's Triad

'Wet, Wacky, Wobbly': 1) Gait disturbance ('magnetic gait', feet glued to floor), 2) Urinary urgency/incontinence, 3) Cognitive impairment

Diagnostic LP Tap Test

NPH: perform timed 10-meter walk test before and after removing 30–50 mL of CSF; objective gait improvement predicts VP shunt success

Bottom-Line Clinical Pearl

Idiopathic Intracranial Hypertension (IIH) presents in young, overweight women of childbearing age with daily headaches, pulsatile tinnitus ('whooshing' sound synchronized with heartbeat), and transient visual obscurations. Physical exam reveals bilateral papilledema and unilateral/bilateral cranial nerve VI (abducens) palsies due to increased ICP stretching the long intracranial nerve course. Neuroimaging (MRI + MRV) must precede lumbar puncture to rule out venous sinus thrombosis and mass lesions. LP confirms elevated opening pressure (> 25 cmH2O in adults) with normal CSF constituents. First-line medical therapy is Acetazolamide (500–1,000 mg BID); urgent optic nerve sheath fenestration or CSF shunting is mandatory if visual fields are deteriorating to prevent irreversible optic atrophy. Normal Pressure Hydrocephalus (NPH) presents in the elderly with the classic triad 'Wobbly, Wet, Wacky' (gait ataxia precedes dementia/incontinence); diagnostic high-volume tap test (30–50 mL CSF removal) demonstrating gait speed improvement confirms candidacy for a ventriculoperitoneal (VP) shunt.

1. Idiopathic Intracranial Hypertension (IIH/Pseudotumor Cerebri)

Idiopathic Intracranial Hypertension (IIH) is characterized by elevated intracranial pressure without ventriculomegaly or intracranial mass lesions. It occurs predominantly in overweight women of childbearing age (female-to-male ratio 8:1). Known secondary pharmacological triggers include: tetracycline antibiotics (doxycycline, minocycline), hypervitaminosis A (retinoids, isotretinoin), growth hormone, and sudden corticosteroid withdrawal.

Modified Dandy Diagnostic Criteria	Diagnostic Thresholds & Clinical Findings
1. Symptoms of Elevated ICP	Progressive daily headache (throbbing, worse when supine or with Valsalva), pulsatile tinnitus (synchronous whooshing sound), and transient visual obscurations (brief 2–5 second 'blackouts' of vision when standing).
2. Objective Signs of Elevated ICP	Bilateral papilledema on fundoscopy (blurring of optic disc margins, flame hemorrhages, absence of spontaneous venous pulsations). Unilateral or bilateral abducens (CN VI) nerve palsy (inability to abduct the eye, producing horizontal diplopia on lateral gaze; acts as a 'false localizing sign').
3. Completely Normal Neuroimaging	MRI Brain + MRV (Venography): completely normal brain parenchyma without mass or hydrocephalus; empty sella turcica, posterior globe flattening, tortuosity of optic nerves with distension of perioptic subarachnoid space; MRV excludes cerebral venous sinus thrombosis (CVST).
4. Elevated CSF Opening Pressure	Opening Pressure > 25 cmH2O in adults (measured via manometer in lateral decubitus position with legs extended); CSF biochemistry and cell count must be entirely normal.

2. Normal Pressure Hydrocephalus (NPH)

Normal Pressure Hydrocephalus is a disorder of elderly adults ($> 65\text{ years}$) characterized by chronic, impaired CSF resorption through arachnoid granulations into the superior sagittal sinus. Over time, ventricular dilation occurs at normal or intermittently elevated mean intracranial pressures, stretching periventricular white matter tracts (corticospinal tracts and sacral bladder fibers).

Hakim's Triad Component	Clinical Characteristics & Chronology	Pathophysiologic Mechanism
1. Gait Disturbance ('Wobbly') — FIRST TO APPEAR	The earliest, most prominent, and most reversible feature. Characterized by a slow, wide-based, short-stepped, shuffling gait where the feet appear stuck to the ground ('magnetic gait'). Turning requires multiple hesitant steps.	Mechanical stretching and compression of the medial paracentral motor fibers of the corona radiata that supply the lower extremities.
2. Urinary Incontinence ('Wet')	Begins as urinary urgency and increased frequency, progressing to urge incontinence and eventually frontal lack of concern regarding incontinence.	Compression of the descending sacral parasympathetic inhibitory fibers from the medial frontal cortex.
3. Dementia/Cognitive Decline ('Wacky')	Subcortical dementia: psychomotor slowing, apathy, impaired attention, executive dysfunction, and forgetfulness; language and praxic skills are typically preserved (distinguishing it from Alzheimer's).	Distortion of frontosubcortical and striatofrontal neural pathways.

Clinical Caution

THE HIGH-VOLUME TAP TEST (NPH): The diagnosis of shunt-responsive NPH is established via a diagnostic high-volume lumbar puncture: quantitatively test the patient's gait speed (10-meter walk test and 'timed up and go' [TUG] test) before and 1 to 2 hours after removing 30 to 50 mL of CSF. An objective improvement in walking speed, step height, or cadence confirms clinical responsiveness and predicts a > 80% success rate with ventriculoperitoneal (VP) shunt placement.

Board & Shelf Drill 5 Questions • Untimed Tutor Mode

Test Your Idiopathic Intracranial Hypertension & Normal Pressure Hydrocephalus Clinical Acumen

Directly launch an active-recall practice block from our 8,400+ validated COMLEX Level 1, 2-CE & 3 board question bank with complete explanations.

Related Emergency Protocols & Differentials

Related EM Protocol