01Approach to the Critical Patient/attcp55

Immediate threats

›Fulminant IIH recognition

›Rapid vision loss within 4 weeks of symptom onset

›Constitutes a neuro-ophthalmologic emergency

›Requires emergent neurosurgical and neuro-ophthalmology consultation

›High-grade papilledema with reduced visual acuity

›Frisén grade IV or V

›Threatened optic nerve function

›Rapidly deteriorating visual fields

›Concentric constriction progressing over days

›Central visual acuity decline

›Elevated ICP emergency features

›Altered consciousness or vomiting from acute ICP surge

›Emergent CT head to exclude herniation

›Neurosurgery activation

›CSF rhinorrhea or otorrhea

›Skull base CSF leak complicating IIH

›ENT and neurosurgery involvement

›New focal neurologic deficits beyond CN VI

›Suggests alternative or secondary cause

›Emergent MRI brain

Stabilization priorities

›Acute ICP reduction

›Therapeutic lumbar puncture: remove 30-40 mL CSF acutely

›Measure opening pressure in lateral decubitus position

›Provides rapid symptomatic relief

›Head of bed elevation 30 degrees

›Reduces venous pressure contribution to ICP

02History/hx72

Presenting symptoms

›Headache characteristics

›Present in 84% of cases

›Often constant or daily

›Morning predominance

›Valsalva worsening

›Coughing, straining, bending

›Positional component

›Absence of positional improvement when supine distinguishes from intracranial hypotension

›Visual symptoms

›Transient visual obscurations in 68%

›Brief graying or blackout of vision

›Often positional

›Persistent blurred vision or visual field loss in 32%

›Indicates significant optic nerve involvement

›Diplopia in 18%

›Horizontal, from CN VI palsy

›Pulsatile tinnitus

›Present in 52%

›Pulse-synchronous whooshing sound

›Laterality: unilateral vs bilateral

›Other neurological symptoms

›Neck and back pain in 53%

›Cognitive complaints: memory and concentration difficulty

›Photopsia or photophobia

Alarm features

›High-risk presentations requiring urgent workup

›Rapidly progressive vision loss

›Loss within days to weeks of symptom onset

›Fulminant IIH variant

›Severe worsening headache unresponsive to analgesia

›Altered mental status, nausea, or vomiting suggesting acute ICP rise

›Atypical demographics raising secondary cause concern

›Male sex, non-obese, elderly, or pediatric patient

›Increases suspicion for cerebral venous sinus thrombosis

›Mandates exclusion of mass lesion and meningitis

›New CN VI palsy with worsening diplopia

›Focal neurologic deficits beyond CN VI

Risk factors

›Obesity and metabolic factors

›Obesity present in approximately 90% of cases

›Strongest modifiable risk factor

›Recent weight gain of 5-15% body weight increases risk

›Female sex, reproductive age 20-40 years

›>95% of cases occur in this demographic

›Incidence 19-21 per 100,000 in overweight/obese women aged 20-44

›Medication exposures

›Strongly associated: tetracycline-class antibiotics

›Minocycline, doxycycline

›Strongly associated: vitamin A derivatives

›Isotretinoin, recombinant growth hormone, lithium

›Moderately associated: corticosteroid withdrawal

›Weakly associated: cyclosporine, progestin-only contraceptives, fluoroquinolones

›Comorbidities

›Black ethnicity: associated with increased risk of visual loss

›Anemia: risk factor for visual complications

›Obstructive sleep apnea: secondary cause of intracranial hypertension

›Renal disease, systemic hypertension

›PCOS, thyroid disease, Cushing syndrome

Past medical and medication history

›Prior IIH episodes

›Recurrence rate approximately 16.5%

›Prior LP or CSF diversion procedures

›Prior bariatric surgery

›Headache history

›Comorbid migraine present in approximately 80% of IIH patients

›Significant diagnostic overlap

›Prior migraine treatments trialed

›Medication reconciliation

›Tetracyclines, retinoids, vitamin A supplements

›Growth hormone, lithium

›Corticosteroids recently discontinued

›Functional and social history

›Impact on driving, work, and daily function

›Access to dietary and weight management resources

›Menstrual irregularity as endocrine clue

03Physical Exam/exam49

Fundoscopy

›Papilledema assessment

›Most important physical sign; usually the only finding

›Absent in approximately 5% of cases

›Frisén scale grading

›Grade 0: normal disc

›Grade I: C-shaped halo

›Grade II: circumferential halo

›Grade III: obscuration of major vessels at disc margin

›Grade IV: complete disc obscuration

›Grade V: proptosis of the disc

›Bilateral involvement typical; unilateral papilledema raises alternative diagnosis

Neuro-ophthalmologic exam

›Visual acuity

›Snellen chart

›May be preserved until late disease

›Reduction from baseline is an emergency trigger

›Colour vision testing if optic neuropathy suspected

›Visual fields

›Confrontation fields at bedside

›Enlarged blind spot is classic early finding

›Concentric constriction in advanced disease

›Formal Humphrey perimetry at neuro-ophthalmology

›Pupillary exam

›Relative afferent pupillary defect (RAPD)

›Indicates significant optic nerve damage

›Asymmetric finding

›Extraocular movements

04Differential Diagnosis/ddx38

Life-threatening mimics

›Cerebral venous sinus thrombosis (ICD-10: G08)

›Can mimic IIH exactly with identical presentation

›Excluded by MR venography

›Must be excluded before IIH diagnosis is confirmed

›Risk factors: thrombophilia, OCP use, postpartum, dehydration

›Intracranial mass lesion (ICD-10: D49.6)

›Tumor, abscess, or cyst producing obstructive hydrocephalus

›Excluded by MRI brain with gadolinium

›Focal deficits and asymmetric papilledema increase suspicion

›Meningitis (ICD-10: G00-G03)

›Infectious, carcinomatous, or inflammatory

›Excluded by CSF analysis showing normal composition

›Fever, meningismus, and altered consciousness are clues

›Dural arteriovenous fistula

›Pulsatile tinnitus and elevated ICP can overlap with IIH

›Excluded by formal angiography or MRA

Secondary intracranial hypertension

›Drug-induced intracranial hypertension (ICD-10: G93.2)

›Phenotypically identical to IIH

›Tetracyclines and retinoids most common causes

›Resolves after drug discontinuation

›Malignant hypertension (ICD-10: I10)

›Bilateral papilledema from severely elevated blood pressure

›BP typically >180/120 mmHg

›Differentiated by BP measurement and systemic organ damage

Headache and visual mimics

›Chronic migraine (ICD-10: G43.709)

05Laboratory Tests/lt37

CSF analysis

›Lumbar puncture with opening pressure

›Gold standard for diagnosis

›Opening pressure >=25 cm H2O (250 mm H2O) required for adult diagnosis

›Measure in lateral decubitus position with legs extended

›CSF composition must be normal for IIH diagnosis

›Normal glucose, protein, cell count, cytology

›Elevated protein or cells suggests meningitis or malignancy

›Therapeutic CSF removal: 30-40 mL when opening pressure is elevated

›Provides transient symptomatic relief

›Lasting remission after single LP not uncommon

Hematologic and metabolic tests

›Complete blood count

›Rule out anemia as risk factor for visual loss

›Anemia threshold: hemoglobin <120 g/L women, <130 g/L men

›Leukocytosis may suggest infection as secondary cause

›Basic metabolic panel

›Baseline electrolytes before starting acetazolamide

›Acetazolamide causes bicarbonate wasting and metabolic acidosis

›Serum bicarbonate monitoring during therapy

›Renal function: acetazolamide is renally cleared

›Pregnancy test

›All women of childbearing age

›IIH management differs in pregnancy

›Acetazolamide: caution in first trimester

Endocrine and special tests

›Thyroid function tests

›Hypothyroidism is a secondary cause

06Diagnostic Tests/dt83

Scoring Systems

›Modified Dandy criteria for IIH diagnosis

›Signs and symptoms of raised ICP (headache, nausea, visual obscurations)

›No explanation by neurological examination for findings other than CN VI palsy

›Elevated CSF opening pressure >=25 cm H2O in adults

›>=28 cm H2O in children

›Normal CSF composition

›No cells, normal glucose and protein

›Normal neuroimaging without hydrocephalus, mass, or structural cause

›MRI preferred over CT for evaluation

›No other cause of intracranial hypertension identified

›Frisén papilledema grading scale

›Grade 0: normal optic disc

›No blurring of disc margin

›Grade I: subtle nasal blurring, C-shaped halo

›Grade II: circumferential elevation of disc

›Grade III: obscuration of major vessels at disc margin

›Moderate papilledema, visual field testing essential

›Grade IV: complete disc obscuration

›High-grade papilledema; urgent intervention

›Grade V: proptosis of disc with obscuration of all vessels

›Most severe; surgical emergency

›IIH severity classification

›Mild: headache with low-grade papilledema, preserved visual acuity and fields

›Moderate: moderate papilledema with visual field defects, preserved acuity

›Severe/Fulminant: rapid vision loss within days to weeks

›High-grade papilledema with reduced visual acuity

›Neuro-ophthalmologic emergency requiring emergent surgery

MRI

›MRI brain with and without gadolinium plus MR venography

›First-line imaging for all IIH evaluations

›Superior to CT for evaluating secondary causes

›MR venography excludes cerebral venous sinus thrombosis

›Positive MRI signs of IIH

›Transverse sinus stenosis: present in 94% of patients

›Partially empty sella: pituitary flattened by chronic elevated pressure

›Posterior globe flattening

›Optic nerve sheath distension

›Optic nerve tortuosity

›Cerebellar tonsillar descent (Chiari-like appearance)

›Normal MRI does not exclude IIH

›Diagnosis relies on CSF opening pressure

›MRI rules out secondary causes

›Optical coherence tomography (OCT)

›Quantifies retinal nerve fiber layer (RNFL) thickness

›Useful baseline for monitoring papilledema severity

›Optic atrophy (thin RNFL) indicates irreversible damage

›Serial OCT for treatment response monitoring

›Reduction in RNFL thickness over time suggests improvement

›MR venography protocol

›Time-of-flight or contrast-enhanced MRV

›Identifies cerebral venous sinus thrombosis

›Identifies transverse sinus stenosis pattern of IIH

CT

›CT head without contrast

›Role in ED: acute exclusion of mass lesion, hydrocephalus, hemorrhage

›Adequate for emergent triage

›Inferior to MRI for IIH-specific findings

›CT signs that may be seen in IIH

›Partially empty sella

›Normal ventricle size (important: no hydrocephalus)

›CT venography

›Alternative to MR venography when MRI unavailable

›Requires contrast; evaluates dural venous sinuses

›CT myelography

›Reserved for suspected CSF leak complicating IIH

›Identifies site of CSF rhinorrhea or otorrhea

›Performed by neurosurgery or neuroradiology

Ultrasound

›Optic nerve sheath diameter (ONSD) measurement

›Point-of-care ultrasound technique

›Place linear probe over closed eyelid with gel

›Measure ONSD 3 mm behind globe

›Threshold values for elevated ICP

›ONSD >5 mm suggests elevated ICP

›Threshold values range 4.8-6.3 mm across studies

›Specificity higher than sensitivity

›Utility

›Bedside screening tool in acute presentation

›Not a replacement for LP or MRI

›Useful when LP cannot be performed immediately

›Automated visual field testing (Humphrey perimetry)

›Essential for baseline and serial monitoring

›Enlarged blind spot: classic early pattern

›Concentric constriction in advanced disease

›Arcuate defects in late optic nerve damage

›Repeat every 1-3 months during active treatment

07Disposition/dispo31

Admission criteria

›Criteria for inpatient admission

›Fulminant IIH with rapidly progressive visual loss

›Emergent neurosurgical and neuro-ophthalmology consultation

›ICU-level monitoring if visual acuity rapidly declining

›Severely elevated opening pressure with significant visual compromise

›Planned urgent surgical intervention

›Inability to arrange urgent outpatient neuro-ophthalmology within 1-2 weeks

›Need for temporary CSF drainage or lumbar drain placement

Observation indications

›ED observation criteria

›New diagnosis with moderate papilledema and visual field defects

›Pending neuro-ophthalmology evaluation

›Post-LP monitoring

›Headache, nausea, or positional symptoms following LP

›Initiation of acetazolamide with metabolic concerns

Discharge criteria

›Safe discharge requirements

›Mild papilledema with fully preserved visual acuity and fields

›Frisén grade I-II without visual acuity reduction

›Neuro-ophthalmology follow-up arranged within 1-2 weeks

›Formal visual field testing scheduled

›Acetazolamide prescription initiated and patient counseled

›Reliable patient with clear understanding of return precautions

›No atypical features suggesting secondary cause

Follow-up and transfers

›Outpatient follow-up timeline

›Neuro-ophthalmology within 1-2 weeks for all new diagnoses

08Treatment/t96

Acute interventions

›Therapeutic lumbar puncture

›Immediate ICP reduction

›Remove 30-40 mL CSF

›Provides transient symptomatic relief

›Lasting remission after single LP not uncommon

›Measure and document opening pressure

›Guides urgency of further intervention

›Repeat LP if symptoms recur and definitive treatment pending

›Medication discontinuation

›Immediately discontinue suspected causative medications

›Tetracyclines: stop minocycline, doxycycline

›Retinoids: stop isotretinoin

›Lithium, growth hormone as indicated

›Corticosteroids: do NOT initiate

›No evidence of benefit; promote weight gain

›Contraindicated in IIH management

Medical therapy

›Acetazolamide (first-line)

›Carbonic anhydrase inhibitor reducing CSF production

›Starting dose: 500 mg extended-release twice daily

›Titrate up over days to reduce side effects

›Target dose range: 1-4 g/day

›Side effects to counsel

›Paresthesias: tingling in hands and feet

›Nausea and dysgeusia: carbonated drink taste change

›Metabolic acidosis: monitor serum bicarbonate

›Fatigue and polyuria

›Contraindications

›Sulfonamide allergy (relative)

›Severe renal impairment

›Caution in first trimester pregnancy

›Evidence base

›IIH Treatment Trial (IIHTT): acetazolamide plus diet superior to diet alone

›Class I recommendation for first-line medical therapy

›Topiramate (alternative)

›Alternative carbonic anhydrase inhibitor

›Starting dose: 25 mg daily, titrate by 25 mg weekly

›Target dose: 100-200 mg/day in divided doses

›Additional benefit: promotes weight loss

›Dual mechanism in IIH management

›Side effects: cognitive slowing, word-finding difficulties, kidney stones

›GLP-1 receptor agonists (emerging role)

›Semaglutide and other GLP-1 agonists

›Weight loss and possible direct ICP reduction via CSF secretion inhibition

›Emerging evidence from JAMA Neurology 2025

›Consider for patients requiring weight management alongside IIH treatment

›Not yet a first-line agent; adjunct role

Weight management

›Dietary interventions

›Low-sodium, calorie-restricted diet

›Supported by IIH Treatment Trial

›Cornerstone of long-term management

›Weight loss targets

›5-10% total body weight loss as initial goal

›6% weight loss linked to papilledema resolution

›15-24% may be needed for full disease remission

›Rate: approximately 0.5 kg/week

›Fluid restriction as adjunct

›Bariatric surgery

›Indication: BMI >=35 kg/m2 with failed lifestyle interventions

›Grade A recommendation

›Multicomponent lifestyle intervention preferred for BMI <35

›Diet plus exercise plus behavioral therapy

›Grade B recommendation

›Referral to bariatric surgery team for eligible patients

Surgical interventions

›Optic nerve sheath fenestration (ONSF)

›Preferred when visual loss is primary concern with minimal headache

›Creates opening in optic nerve sheath to decompress optic nerve

›Direct protection against vision loss

›Effective for papilledema and visual field improvement

›Does not reliably treat headache

›For fulminant IIH threatening vision acutely

›CSF shunting procedures

›Ventriculoperitoneal (VP) or lumboperitoneal (LP) shunt

›VP shunt preferred in most centers

›LP shunt: higher revision rate but avoids craniotomy

›Preferred when both visual loss and refractory headache are significant

›Revision surgery required in up to 50% due to shunt failure

›Venous sinus stenting

›Emerging option for significant transverse sinus stenosis

›Trans-stenotic pressure gradient >10 mmHg required on venous manometry

›Reduces venous back-pressure on CSF absorption

›Digital subtraction angiography with venous manometry required preoperatively

›AHA scientific statement: consider for refractory cases with venographic stenosis

›Temporary lumbar drain

›Bridge to definitive surgery in fulminant cases

›Continuous CSF drainage in ICU setting

›Not a long-term solution

Headache management

›IIH-associated headache treatment

›Acetazolamide addresses ICP-driven headache

›Headache may persist even after ICP normalization

›Requires separate migraine-directed therapy if refractory

›Migraine-specific therapy for comorbid migraine

›Triptans for acute attacks

›Topiramate: dual benefit for IIH and migraine prophylaxis

›Avoid opioids and frequent analgesics

›Risk of medication overuse headache

›Can worsen underlying headache disorder

09Special Populations/sp67

Pregnancy

›Physiological considerations

›IIH can develop de novo or worsen during pregnancy

›Weight gain during pregnancy is a contributing factor

›Most commonly presents in first trimester

›Hormonal changes may influence CSF dynamics

›Progesterone and estrogen effects on CSF secretion

›Medication safety

›Acetazolamide: caution in first trimester

›Teratogenic in animal studies; limited human data

›Generally avoided in first trimester; used in later trimesters with monitoring

›Considered safer than untreated vision loss

›Topiramate: teratogenic (oral cleft risk)

›Avoid in pregnancy if possible

›GLP-1 agonists: not recommended in pregnancy

›Insufficient safety data

›Corticosteroids: still contraindicated

›Management approach

›Serial LPs as bridge therapy in first trimester

›Repeated every 1-4 weeks as needed

›Maintains ICP control without teratogenic medications

›Weight management: appropriate gestational weight gain targets

›Optic nerve sheath fenestration preferred surgical option if urgently required

›Safer than shunting in pregnancy

›Multidisciplinary team: neurology, neuro-ophthalmology, maternal-fetal medicine

Geriatric

›Epidemiologic differences

›IIH in elderly patients is less common

›Secondary causes more likely in atypical demographics

›Male sex, non-obese status increase secondary cause probability

›Cerebral venous sinus thrombosis more common in older adults

›Must be rigorously excluded

›Clinical considerations

›Polypharmacy risk: multiple medications may contribute

›Careful medication reconciliation

›Corticosteroid withdrawal more likely after prolonged use

›Comorbidities alter management

›Renal impairment reduces acetazolamide clearance

›Reduced acetazolamide starting dose and careful monitoring

›Vision loss particularly impactful on functional independence

›Falls risk from visual field loss

›Driving assessment required

›Modified treatment targets

›Aggressive weight loss less appropriate in frail elderly

›Nutritional adequacy must be maintained

›Bariatric surgery: high operative risk in elderly with comorbidities

›Individual risk-benefit assessment required

Pediatrics

›Epidemiologic differences

›Prepubertal children: equal sex distribution, often non-obese

›Secondary causes more common than in adults

›Require thorough workup for underlying etiology

›Post-pubertal adolescents: adult phenotype

›Female predominance, obesity association emerges

›Diagnostic thresholds

›CSF opening pressure threshold: >=28 cm H2O in children

›Higher than adult threshold of >=25 cm H2O

›Must be measured in lateral decubitus without sedation if possible

›Sedation raises ICP and may falsely elevate readings

›Modified Dandy criteria applied with age-appropriate thresholds

›Treatment considerations

›Acetazolamide: weight-based dosing

›Starting dose: 15 mg/kg/day divided twice daily

›Maximum: 100 mg/kg/day or adult maximum

›Weight management in obese adolescents

›Multicomponent behavioral intervention

›Bariatric surgery for adolescents with BMI >=40 and severe comorbidities

›Vision outcome: generally better prognosis than adults with appropriate treatment

›Neurodevelopmental impact of chronic headache must be addressed

›School performance and quality of life monitoring

10Background/b67

Epidemiology

›Incidence and prevalence

›General population incidence: 1-2 per 100,000 per year

›Rises to 19-21 per 100,000 in overweight/obese women aged 20-44

›Demographic profile

›>95% of cases: obese women of childbearing age

›Peak incidence: ages 20-40 years

›Rising incidence paralleling obesity epidemic

›Significant public health burden

›Morbidity and outcomes

›Permanent visual field loss occurs in a significant minority

›Severe disability if vision not protected

›Chronic disabling headache is the most common ongoing complaint

›Quality of life significantly impacted

›Depression and anxiety are common comorbidities

›Cardiovascular risk

›IIH patients have >2x cardiovascular event risk vs. BMI-matched controls

›Independent cardiovascular risk factor

›Recurrence rate approximately 16.5%

›Long-term monitoring required

Pathophysiology

›Mechanism of elevated ICP

›Net increase in CSF volume or resistance to outflow

›Arachnoid granulation dysfunction reducing CSF absorption

›Venous hypertension from transverse sinus stenosis

›Venous sinus stenosis theory

›Transverse sinus stenosis present in 94% of patients

›Elevated venous pressure reduces CSF reabsorption gradient

11Patient Discharge Instructions/pdi30

copy discharge instructions

›Discharge instructions for Idiopathic Intracranial Hypertension

›Diagnosis explanation

›IIH means the pressure around your brain is higher than normal without a known structural cause

›This can damage the nerves in your eyes and cause vision loss if untreated

›Treatment focuses on protecting your vision and relieving headaches

›Medications

›Take acetazolamide exactly as prescribed

›Common side effects: tingling in hands and feet, taste changes with carbonated drinks, fatigue

›These are usually tolerable and not dangerous

›Do not stop your medication without talking to your doctor

›Weight management

›Weight loss is the most important long-term treatment for IIH

›Even 5-10% of body weight lost can significantly improve your condition

›Your doctor or dietitian will guide a safe weight loss plan

›Activity and restrictions

›You may resume normal daily activities unless your vision is affected

›Do not drive if your vision is impaired or if you are having visual blackouts

›Avoid activities that significantly raise your head pressure: heavy lifting, straining

›Follow-up appointments

›Eye specialist (neuro-ophthalmologist) within 1-2 weeks

›This appointment is essential to protect your vision

›Bring your glasses or contact lenses to the appointment

›Repeat vision testing every 1-3 months while on treatment

›Return to emergency department immediately for

›Any new or worsening vision loss or blurred vision

›Increasing frequency of brief visual blackouts (transient visual obscurations)

›New double vision

12References/r36

Guidelines and key sources

›Primary evidence sources

›Horton JC. Idiopathic Intracranial Hypertension. New England Journal of Medicine 2025

›Comprehensive review: epidemiology, diagnosis, management

›NEJM reference: 10.1056/NEJMra2404929

›Sioutas GS et al. GLP-1 Receptor Agonists in Idiopathic Intracranial Hypertension. JAMA Neurology 2025

›Emerging pharmacotherapy evidence

›IIH Treatment Trial (IIHTT)

›Acetazolamide plus low-sodium diet vs. diet alone

›Foundation for first-line medical management

›Ball AK, Clarke CE. Idiopathic Intracranial Hypertension. Lancet Neurology 2006

›Landmark review establishing diagnostic and treatment standards

›Supporting references

›Kilic K et al. Diagnosis of IIH: Importance of Excluding Secondary Causes. Cephalalgia 2022

›Systematic review of secondary causes and diagnostic pitfalls

›Barkatullah AF et al. MRI Findings as Markers of IIH. Current Opinion in Neurology 2021

›MRI sign prevalence and diagnostic utility

›Tan MG et al. Drug-Induced Intracranial Hypertension. Am J Clin Dermatol 2020

›Systematic review of drug causes; tetracyclines and retinoids

›Abbott S et al. Weight Management Interventions for Adults with IIH. Neurology 2023

›Systematic review; bariatric surgery Grade A, lifestyle Grade B

›Adderley NJ et al. IIH and Cardiovascular Disease Risk in Women. JAMA Neurology 2019

›>2x cardiovascular event risk in IIH vs. BMI-matched controls

›Olaru C et al. Increased Intracranial Pressure in the Emergency Department. West J Emerg Med 2024

›Emergency medicine perspective on ICP evaluation

›Bouffard MA. Fulminant IIH. Current Neurology and Neuroscience Reports 2020

›Fulminant variant: rapid visual loss, surgical management

›Eskey CJ et al. Indications for Intracranial Endovascular Procedures. AHA Scientific Statement. Circulation 2018

Evidence & Review

Evidence & Review