Idiopathic intracranial hypertension (IIH)

General

Pseudotumor cerebri (PTC)
Idiopathic intracranial hypertension
Benign intracranial hypertension

As far as neurosurgery is concerned

If there no vision problems (papillodema) then get the neurologist and/or ophthalmologist to manage

In general, the term pseudotumor cerebri is preferred because it encompasses cases where there is a known etiology as well as idiopathic cases (the concept of “secondary idiopathic intracranial hypertension” is an oxymoron).

Some, but not all, authors exclude patients with intracranial hypertension in the presence of dural sinus thrombosis.

There is a juvenile and an adult form

Definition

Is a condition characterized by increased ICP with no evidence of intracranial mass, hydrocephalus, infection (e.g. meningitis, especially chronic ones such as fungal meningitis), or hypertensive encephalopathy.

A diagnosis of exclusion

Term	Definition
Adult	All patients above the age of 16 years old for the purpose of this statement.
Idiopathic intracranial hypertension (IIH)	Patients with raised ICP of unknown aetiology fulfilling the criteria set out in figure 1.
Fulminant IIH	Patients meeting the criteria for a precipitous decline in visual function within 4 weeks of diagnosis of IIH.
Typical IIH	Patients who are female, of childbearing age and who have a body mass index (BMI) greater than 30 kg/m².
Atypical IIH	Patients who are not female, or not of childbearing age or who have a BMI below 30 kg/m². These patients require more in-depth investigation to ensure no other underlying causes (table 2).
IIH without papilloedema	A rare subtype of IIH and is seen in patients who meet all the criteria of definite IIH, seen in figure 1, in the absence of papilloedema. The criteria have highlighted the importance of a pressure greater than 25 cm CSF and the necessity for additional features, which suggest pathologically raised ICP. Features such as sixth nerve palsy and MRI imaging features indicating raised ICP should be sought (box 1).
IIH in ocular remission	Patients that have been diagnosed as IIH, and the papilloedema has resolved. These patients may have ongoing morbidity from headache, but their vision is no longer at risk while there is no papilloedema.

Epidemiology

Incidence

In general population 2.4/100,000
In obese women of childbearing years: 20/100,000

Peak incidence in 3rd decade (range: 1–55 years)
Children

Very rare in infancy
37% of cases are in children,
90% of these are age 5–15 years.

Gender

Female: male ratio:2:1 to 8:1
No gender difference in juvenile form
Not as prevalent in men

Obesity is reported in 11–90% of cases

Frequently self limited

Recurrence rate: 9–43%

Visual deficit

Severe visual deficits develop in 4–12%
Unrelated to

Duration of symptoms,
Degree of papilledema,
Headache,
Visual obscuration,
Number of recurrences.

Perimetry is the best means to detect and follow visual loss

Pathogenesis

Not fully understood.

Theories

Increased cerebral oedema & brain water content,
Increased venous pressure & cerebral blood volume,
Reduced CSF absorption

High prevalence in obese females

Mechanical theory

Obesity → ⬆️ intraabdominal pressure → ⬆️ central venous pressure → ⬇️ CSF resorption → ⬆️ ICP

However, other studies have indicated that elevated venous pressure may actually be an epiphenomenon to a primary increase in ICP

Hormonal theory

Adipocytes convert androstenedione → estrone → ⬆️ CSF production

Risk factors

Metabolic disease

Cushing's,
Addison's,
Hypothyroidism,
PCOS,
CKD

OSA, SLE, anemia, Lyme disease
Drugs

Retinoids
Tetracyclines
Growth hormone
Lithium
Corticosteroids
Contraceptives

Diagnostic criteria

Modified Dandy’s diagnostic criteria

CSF pressure

> 20cm H₂O

Pressures > 40 are not uncommon.

Some recommend that the pressure should be > 25 to exclude normal.
Diurnal variations in CSF pressure may occasionally cause a falsely low (i.e., normal) reading.

∴ If clinical suspicion is high, an LP at a different time of day or continuous ICP monitoring may be required

CSF composition

Normal glucose and cell count.
Protein is normal, or in ≈ two thirds of cases it is low (< 20mg%)

Symptoms & signs

Due to elevated ICP alone (i.e., papilledema & H/A) with no focal findings.
Allowed exception: abducens nerve palsy which may be due to increased ICP

Normal radiologic studies of the brain (CT or MRI) with the allowed exceptions of

The occasionally seen slit ventricles (the incidence may be no higher in PTC than in age matched controls) or empty sella
Infantile form may have generous ventricles and large fluid spaces over brain
Intraorbital abnormalities may be identified: see below

IIH diagnostic criteria (Friedman diagnostic criteria)

Elevated lumbar puncture pressure ≥ 25cm H₂O

Papilledema

Normal neurological examination (except sixth cranial nerve palsy)

Neuroimaging

Normal brain parenchyma (no hydrocephalus mass, structural lesion or meningeal enhancement).
Venous thrombosis excluded in all.

Normal CSF constituents

IIH without papilledema (IIHWOP) diagnostic criteria

Elevated lumbar puncture pressure ≥ 25cm H₂O

Unilateral or bilateral CN6 palsy

Normal neurological examination

Neuroimaging

Normal brain parenchyma (no hydrocephalus mass, structural lesion or meningeal enhancement).
Venous thrombosis excluded in all.

Normal CSF constituents

Suggestion of possible IIHWOP if

Normal neurological examination

Neuroimaging

Normal brain parenchyma (no hydrocephalus mass, structural lesion or meningeal enhancement).
Venous thrombosis excluded in all.

3 neuroimaging finding suggestive of raised intracranial pressure

Empty sella
Flattening of posterior aspect of the globe
Distention of the perioptic subarachnoid space ± a tortuous optic nerve
Transverse venous sinus stenosis

Normal CSF constituents

Elevated lumbar puncture pressure ≥ 25cm H₂O

Associated conditions

General information

Some cases of PTC are idiopathic (IIH).

“IIH” can be sometimes secondary to some other condition

Transverse sinus thrombosis

Many conditions cited as being associated with PTC may be coincidental.

Four criteria suggested to establish a cause-effect relationship

Meets Dandy’s criteria
Condition should be proven to increase ICP
Treatment of the condition should improve the pseudotumor cerebri
Properly controlled studies should show an association between the condition and PTC

Likelihood of association between various conditions and PTC based on the number of the criteria met in

Proven association	Meets 4 criteria from Table 47.2
ㅤ	Obesity
Likely association	Meets 3 criteria from Table 47.2
ㅤ	Drugs: keprone, lindane
ㅤ	Hypervitaminosis A
Probable association	Meets 2 criteria from Table 47.2
ㅤ	Steroid withdrawalᵃ
ㅤ	Thyroid replacement in children
ㅤ	Ketoprofen & indomethacin in Bartter syndrome
ㅤ	Hypoparathyroidism
ㅤ	Addison’s diseaseᵃ
ㅤ	Uremia
ㅤ	Iron deficiency anemia
ㅤ	Drugs: tetracycline, nalidixic acid, Danazol, lithium, amiodarone, phenytoin, nitrofurantoin, ciprofloxacin, nitroglycerin
Possible association	Meets 1 criterion from Table 47.2
ㅤ	Menstrual irregularity
ㅤ	Oral contraceptive useᵇ
ㅤ	Cushing’s syndrome
ㅤ	Vitamin A deficiency
ㅤ	Minor head trauma
ㅤ	Behçet syndrome
Unlikely association	Meets none of the criteria in Table 47.2
ㅤ	Hyperthyroidism
ㅤ	Steroid use
ㅤ	Immunization
Unsupported association	Pregnancy
ㅤ	Menarche

ᵃMay respond to steroids
ᵇMay be associated with dural sinus thrombosis, see text

Other conditions not included in this list that meet minimal criteria but are unconfirmed in case control studies include

Other drugs: isotretinoin (Accutane®), trimethoprim-sulfamethoxazole, cimetidine, tamoxifen
Systemic lupus erythematosus (SLE)

Conditions that may be related by virtue of increased pressure in the dural sinuses (see below)

Otitis media with petrosal extension (so-called otitic hydrocephalus)
Radical neck surgery with resection of the jugular vein
Hypercoagulable states

Associations that have been reported as causing raised Intracranial pressure

Haematological	Anaemia, Polycythaemia vera
Obstruction to venous drainage	Cerebral venous sinus thrombosis
ㅤ	Jugular vein thrombosis
ㅤ	Superior vena cava syndrome
ㅤ	Jugular vein ligation following bilateral radical neck dissection
ㅤ	Increased right heart pressure
ㅤ	Arteriovenous fistulas
ㅤ	Previous infection or subarachnoid haemorrhage causing decreased CSF absorption
Medications	Fluoroquinolones
ㅤ	Tetracycline class antibiotics
ㅤ	Corticosteroid withdrawal
ㅤ	Danazol
ㅤ	Vitamin A derivatives (including isotretinoin and all-transretinoic acid)
ㅤ	Levothyroxine
ㅤ	Nalidixic acid
ㅤ	Tamoxifen
ㅤ	Ciclosporin
ㅤ	Levonorgestrel implant
ㅤ	Lithium
ㅤ	Growth hormone
ㅤ	Indomethacin
ㅤ	Cimetidine
Systemic disorders	Chronic kidney disease/renal failure
ㅤ	Obstructive sleep apnoea syndrome
ㅤ	Chronic obstructive pulmonary disease
ㅤ	Systemic lupus erythematosus
ㅤ	Psittacosis
Endocrine	Addison’s disease
ㅤ	Adrenal insufficiency
ㅤ	Cushing’s syndrome
ㅤ	Hypoparathyroidism
ㅤ	Hypothyroidism
ㅤ	Hyperthyroidism
Syndromic	Down syndrome
ㅤ	Craniosynostosis
ㅤ	Turner syndrome

Natural history

Spontaneous resolution is common, sometimes within months, but usually after ≈ 1 year.

Papilledema persists in ≈ 15%.

Permanent visual loss occurs in 2–24% (depending on criteria used and degree to which it is sought).

Persistent H/A may occur in some.

Recurs in ≈ 10% after initial resolution.

Clinical features

Symptoms

Classic (major) symptoms

H/A (the most common symptom): 94–99%.

Typically retro-ocular and pulsatile.
May ⬆️ with eye movement.
Severity does not correlate with degree of CSF pressure elevation.
Occasionally worse in A.M.
Headache attributed to IIH (International Classification of Headache Disorders, 3rd edition)

(A) Any headache fulfilling criterion C

(B) IIH has been diagnosed with lumbar puncture pressure ≥ 25cm CSF

Headache developed in temporal relation to IIH

Headache relieved by reducing ICP

Headache exacerbated in temporal relationship to increased ICP

(D) Headache not accounted for by another ICHD-3 diagnosis

Nausea: 32% (actual vomiting is less common)

Visual loss (PTC below)

Transient visual obscuration (TVO)
Permanent afferent visual pathway injury

Diplopia (more common in adults, usually due to VI nerve palsy): 30%

Minor symptoms

Neck stiffness: 30–50%

Tinnitus

The causal relationship with PTC has been demonstrated by resolution of these symptoms with reduction of CSF pressure
Up to 60%.
Usually pulse synchronous.
Described as rushing noise.
May be unilateral

In these, may be reduced by ipsilateral jugular vein compression + ipsilateral head rotation

Ataxia: 4–11%

Acral paresthesias: 25%

Retrobulbar eye pain on eye movements

Arthralgia: 11–18%

Dizziness: 32%

Fatigue

Reduced olfactory acuity

Worsening of any of the above symptoms with postural changes that increase ICP

(Bending over, Valsalva maneuver…) is characteristic in idiopathic intracranial hypertension.

Signs

Signs are generally restricted to visual system.

Conspicuously absent: altered level of consciousness in spite of high ICP

Eye findings

Papilledema

Present in almost ≈ 100%

Usually bilateral, occasionally unilateral

May be mild (subtle nerve fibre elevation)

Abducens nerve (Cr. N. VI) palsy

20%;

A false localizing sign

The esotropia ranges from <5 prism diopters dysconjugate angle in primary gaze to > 50

Visual acuity

Relatively insensitive assessment of visual function

Visual field defect

Early changes: peripheral fields & nasal quadrant defect

Enlarged blind spot (66%) and concentric constriction of peripheral fields (blindness is very rare at presentation)

Nerves are being stretched over a swollen optic disc causing arcuate scotoma

Visual loss

General information

Quoted range of occurrence in PTC

48–68% (lower numbers generally come from population-based samples).
A prospective study found changes by Goldman perimetry in 96% of 50 patients.
The only parameter associated with worsening vision is recent weight gain.

Pathomechanics

Increased ICP is transmitted along optic nerve sheath → circumferential compression of the retinal ganglion cell axons at the level of the lamina cribrosa.

Manifestations

Transient visual obscuration's (TVO)

Graying or blacking out of vision.

Lasts ≈ 1 second.

Uni- or bilateral.

Typically occur with eye movement, bending over, or Valsalva manoeuvre.

Directly proportional to severity of papilledema.

Frequency of TVOs parallels ICP elevation, but doesn’t correlate with permanent visual loss

Visual loss in PTC

May occur early or late,

May be sudden or gradually progressive,

Is not reliably correlated to

Duration of symptoms,
Papilledema,
H/A,
Snellen visual acuity, or
Number of recurrences.

It may escape detection until profound.

Time

Early

Usually constriction of fields and loss of color (∴ perimetry is the best test for following vision in PTC)

Late

Central vision is affected.

Findings include: concentric constrictions, enlargement of the blind spot, inferior nasal defects, arcuate defects, cecocentral scotomas…

Infantile form may have only enlarging OFC, frequently self-limited, usually requires only follow up without specific treatment

Evaluation

Overview: Most tests are intended to rule out conditions that may mimic (or produce) PTC

Cerebral imaging: cerebral CT or MRI (see below) scan without and with contrast

Measure opening pressure (OP) with patient in lateral decubitus position
CSF analysis to rule out infection (e.g. fungus, TB, or Lyme disease), inflammation (e.g. sarcoidosis, SLE), or neoplasm (e.g. carcinomatous meningitis)

Protein/glucose
Cell count
Routine & fungal cultures
Cytology if suspicion of carcinomatous meningitis

Routine labs

CBC, electrolytes, PT/PTT
W/U for sarcoidosis or SLE if other findings suggestive (e.g. cutaneous nodules, hypercoagulable state…)

Neuro-ophthalmologic

Visual field testing using quantitative perimetry, with evaluation of size of blind spot,

Slit-lamp examination ± fundus photographs

Look for continuous venous pulsation

BP to R/O malignant HTN → hypertensive encephalopathy

CT

CT without and with IV contrast

Is usually adequate to R/O intracranial mass as a possible cause of intracranial hypertension,
May miss cases of dural sinus thrombosis.

MRI & MRV are preferred.

MRI

See Antona 2021

Intracranial abnormalities are usually absent or minimal

No structural mass lesion

Features of raised intracranial pressure

Slit ventricles

Empty Sella in 30– 70%

Intraorbital findings may be more substantial and include

Flattening of the posterior sclera (red dash): 80%
Enhancement of the prelaminar optic nerve: 50%

Protrusions of the optic nerve heads (red arrows)

Distention of the perioptic subarachnoid space (yellow): 45%
Vertical tortuosity of the orbital optic nerve: 40%
Intraocular protrusion of the prelaminar optic nerve: 30%

Venography

MR venography (MRV) has largely replaced conventional venography to rule out dural sinus or venous thrombosis.

Right transverse sinus is not filling

Stenosis of transverse sinus is due to raised ICP rather than a cause of IIH

Intracranial venous pressure monitoring

Measure pressure across the stenosis >8-10mmHg difference → stenting

Helps with headaches and lowers pressures

Management

See Mollan et al 2018

Aims

Treat the underlying disease

Protect the vision

All patients must have repeated thorough ophthalmologic exams

Minimise the headache morbidity.

Stop possible offending drugs

e.g. vitamin A

Lifestyle changes

Weight loss

General information

Weight loss is the only disease-modifying therapy in typical IIH

All patients with a BMI >30 kg/m2 should be counselled about weight management at the earliest opportunity

How much weight should be lost

Do not know
A weight loss of 6% usually results in complete resolution of papilledema.
The year preceding a diagnosis of IIH is associated with 5%–15% wt gain,
15% of weight loss was required to put IIH into remission in one cohort

However, resolution may be too slow for acutely threatened vision.

Symptoms recur if the weight is regained

Methods

Dieting: uncontrolled studies suggest that this is effective, but it is rarely accomplished or sustained

Bariatric surgery: gastric bypass, laparoscopic banding…

Treat underlying disease

Support weight loss for overweight IIH patients
Bariatric surgery

See Mollan 2022

Evidence

IHH weight trial : RCT bariatric surgery vs community weight management

Women with idiopathic intracranial hypertension and a body mass index of 35 or higher

Intracranial pressure measured by lumbar puncture opening pressure at 12 months

Bariatric surgery was superior to a community weight loss in lowering intracranial pressure and this is sustained even at 2 years

Management recommendations for specific situations

PTC patients with H/A and no visual loss

Neurology treatment: medical therapy to control ⬆️ ICP and H/A. ONSF not recommended.

Shunting is an option if medical management fails

PTC with visual loss without H/A

Mild visual loss: acetazolamide 500–1500 mg/d, follow-up q 2 weeks

Moderate visual loss: acetazolamide 2000–3000mg/d, follow-up q week

Severe visual loss, moderate visual loss that doesn’t respond to acetazolamide, or optic disc at risk

Methylprednisolone 250mg IV q 6 hrs + acetazolamide 1000mg PO BID
If no improvement: ONSF. Consider shunt if ICP > 300mm H₂O

PTC with visual loss AND H/A: for patients with surgical indications, either surgical procedure is appropriate. Shunting may relieve both problems simultaneously. ONSF may be more reliable to relieve the visual problems (the failure rate may be lower than the shunt malfunction rate) but is not as good for the H/A

IIH W/O Papilledema

Symptomatic treatment for H/A, diuretics

PTC in children and adolescents

May be seen with withdrawal of steroids used for asthma

Search for and correction of underlying Aetiology (offending drugs listed above, hypercalcemia, cancer…)

Acetazolamide has been used with success

PTC in pregnancy

Women who first present with PTC during pregnancy: resolution of PTC following delivery is common

Women who become pregnant during therapy

1st trimester

Observation
Limitation of weight gain
Serial LPs.
❌ Acetazolamide should be avoided because of teratogenicity

2nd & 3rd trimester: acetazolamide has been used safely, but involvement of high-risk obstetrician specialist is advised

Pseudopapilledema

(Associated with drusen, etc., in the absence of intracranial hypertension): no interventions.

Reassurance and H/A management are employed

Acute exacerbation of H/A in IIH with known CSF shunt in situ

Evaluation

For all shunted patient with IIH presenting with an acute exacerbation of headaches, funduscopy is mandatory to establish if papilledema exists and where visual function (including formal visual fields) is documented to be worsening, then surgical intervention may be required.

For those with atrophic optic nerves further care should be taken to establish whether the headache is secondary to raised intracranial pressure.

In those where there is suspicion of infection that may be worsening the headache, CSF should be obtained for microbiological evaluation and any underlying resultant infection appropriately treated.

If no papilledema

Do not do diagnostic lumbar puncture

Unless suspicion of infection

Do not routinely CT imaging or shunt X-ray

As it won't change management

In those with papilledema, some may choose to perform a diagnostic LP.

This may be helpful to establish ICP level and may have implications for management choices.

In some ICP, monitoring may be useful.

Treatment

For patients without current papilledema or imminent risk to vision, shunt revision is not recommended.

In shunted patients with deteriorating headaches, low pressure headache and shunt over drainage should be considered.

In established over-drainage or low CSF pressure, consideration should be given to the valve settings or tying the shunt off.

In the absence of shunt over drainage headache management should be done instead → neurologist

Consider medication overuse headache as a cause of acute exacerbation in shunted patients.

Treatment

General information

Treatment of asymptomatic PTC patients is controversial as there is no reliable predictor for visual loss.

Close follow-up with serial formal visual field evaluation is necessary.
Intervention is recommended in unreliable patients, or whenever visual fields deteriorate.

It is possible to lose vision without H/A or papilledema

Most cases remit by 6–15 weeks, but relapse is common

Medical treatment

Fluid and salt restriction

Diuretics

Slows CSF production
Options

Carbonic anhydrase (CA) inhibitors

Acetazolamide

Start at 125–250mg PO q 8–12 hrs, or long acting Diamox Sequels® 500mg PO BID. → Increase by 250mg/day until symptoms improve, side effects occur, or 2 g/day reached.

Side effects: (in high doses)

Acral paraesthesia (limbs)
Nausea
Metabolic acidosis
Altered taste
Renal calculi
Drowsiness
Rare

Stevens-Johnson syndrome
Toxic epidermal necrolysis
Agranulocytosis

With allergy to sulfa
History of renal calculi

Evidence

IIH treatment trial 2014

N = 165
Low-sodium weight-reduction diet + maximally tolerated dosage of acetazolamide (up to 4 g/d) VS
Placebo
6 months.
In patients with IIH and mild visual loss, the use of acetazolamide with a low-sodium weight-reduction diet compared with diet alone resulted in modest improvement in visual field function.

Methazolamide

Better tolerated but less effective.

50–100mg PO BID-TID.

Side effects: similar to acetazolamide

Topiramate

Mechanism

Anticonvulsant with secondary inhibition of CA.

200mg PO BID.

Side effects

Similar to acetazolamide, but can be used in sulfa allergic patients

Furosemide

Start: 160mg per day in adults, adjust per symptoms and eye exam (not to CSF pressure)

If ineffective, double (320 mg/day)

Monitor K+ levels and supplement as needed

Steroids

Used if the above 2 treatment is if ineffective
Options

Dexamethasone (Decadron®) 12mg/day
Prednisone 40– 60mg/day, or
Methylprednisolone 250mg IV q 6 hrs.

May ⬆️ CSF resorption in cases of inflammation or venous thrombosis.

Can be used as temporizing agents for patients awaiting surgery.

A reduction in symptoms should occur by 2 weeks, after which time the steroid should be tapered over 2 weeks.

Long-term use is not recommended due to (among other things) associated weight gain

Managing h/a

A neurologist JOB
Do not use opioids

Lead to opioid induced h/a

Short term pain killers for few weeks

NSAIDs

Indomethacin

Paracetamol

Acetazolamide has not been shown to be effective for the treatment of headache alone
CSF diversion is generally not recommended as a treatment for headache alone in IIH

Surgical therapy

Indication

For cases refractory to above, OR

Visual loss is progressive or is severe initially OR

Unreliable patient

DO NOT DO IT FOR MANAGING H/A

CSF diversion procedures for the management of headaches should only be carried out in a multidisciplinary setting and following a period of intracranial pressure monitoring.

Serial LPs until remission

Serial lumbar punctures are NOT recommended for management of IIH.

LPs are associated with significant anxiety in many patients
Can led to acute and chronic back pain in some patients

Relief of headache in nearly three quarters of patients,

25% remit after 1st LP

Technique

Remove up to 30ml to halve OP, perform qod until OP< 20cm H₂O, then decrease to q wk (no patient who had remission by 2nd LP had OP>350 on 1st LP).
Use a large gauge needle (e.g. 18 Ga) which may help promote a post-LP CSF leak into subcutaneous tissues.

LPs may be difficult in obese patients.

Revisions may be required in up to 50%.

Side effects: include sciatica from nerve root irritation, acquired cerebellar tonsillar herniation, spinal H/A (from intracranial hypotension)

Shunts

VP shunt

Preferred

Has the lowest revision rate amongst all the other shunts

Often difficult since the ventricles are frequently small or slit-like.

Stereotactic techniques may make this more technically feasible.

Adjustable valves with antigravity or antisiphon devices should be considered for use to reduce the risk of low pressure headaches

Start with high pressures and titrate down

To prevent subdurals

If still having headache after all available titration tell the patient that is all you can do

Outcome

50% revision rate
Papilledema improves in 50%
Headache improves in 70% but may recur

Lumbar shunt

Lumboperitoneal;

May be difficult in obese patient.
May need a horizontal-vertical valve to prevent H/A from intracranial hypotension.

Lumbopleural shunt.

Visual loss has been reported in patients with functioning LP shunts.
Complications

Back pain
Radiculopathy
Tonsillar herniation
Scoliosis

Cisterna magna shunt

May shunt to vascular system

Optic nerve sheath fenestration

Mainly for vision protection and reversal of papilledema

Better than shunt in protecting vision (not RCT).

Shunt is better than ONSF in helping with headaches as well.

No indicated when papilledema has resolved
Not for treat other symptoms (e.g. H/A).

1/2 patients show not improvement to h/a

Technique

Performed via medial or less commonly a lateral orbitotomy or transconjunctival medial approach.

Has succeeded in cases where visual loss progressed after LP shunting, possibly due to poor communication between orbital and intracranial subarachnoid spaces.

Bilateral improvement in vision often occurs after a unilateral procedure

May reverse or stabilize visual deterioration and sometimes (but not always) lowers ICP (by continued CSF filtration) and may protect the contralateral eye (if not, contralateral ONSF must be performed).

Side effects

Pupillary dysfunction,
Peripapillary haemorrhage
Chemosis,
Chorioretinal scarring,
Diplopia (usually self-limited) from medial rectus disruption.

Outcome

25% revision rate
Papilloedema improves in 90%
Headache improves in 50%
Treatment failure rates

34% of patients at 1 year
45% at 3 years

Decompressive craniectomy

Options

Subtemporal decompression (main)
Suboccipital decompression.

Subtemporal decompression

Older treatment advocated by Dandy.
Fell out of favour (due to because of risk of post-op seizures and painful bulging at decompression site),
Can be indicated in patients with slit ventricles and in whom lumbar-peritoneal shunting is not feasible.
Usually bilateral “silver-dollar size” craniectomies (approximately 1 inch= 25.4mm) under the temporalis muscle to floor of middle fossa; open dura, cover brain with absorbable sponge (e.g. Gelfoam®), close fascia and muscle watertight, anticonvulsants were started due to risk of post-op seizures.
Kessler et al used larger 6–8cm diameter unilateral craniectomies; this larger craniectomy may explain their high incidence (62%) of H/A and tense bulging decompression sites necessitating CSF diversion.

Interventional procedures

Venous sinus stenting may be considered for refractory cases.

Neurovascular stenting is not currently a treatment for headache in IIH

Controversial

Transverse sinus stenosis may be an epiphenomenon as a result of increased ICP and not the cause of the increase.
Requires antiplatelet therapy afterwards, which may preclude other intervention (e.g. shunting) if it fails

Follow up

At least 2 years (with repeat imaging, e.g. MRI) to R/O occult tumour

Differential diagnosis

True mass lesions

Tumour, cerebral abscess, subdural hematomas, rarely gliomatosis cerebri may be undetectable on CT and will be misdiagnosed as PTC

Cranial venous outflow impairment

Some authors consider these as IIH,18 others do not

Dural sinus thrombosis

Venous hypertension has often been proposed as a unifying underlying cause of PTC.
Abnormalities of the dural sinuses

Thrombosis,
Stenosis,
Obstruction
Elevated pressure (reaching levels as high as 40mm Hg)

While these findings may underlie a significant number of cases, they may in actuality be epiphenomena (e.g. venous hypertension may be due to compression of the transverse sinuses by elevated intracranial pressure), and it is unlikely that such abnormalities will explain all cases.

Congestive heart failure

Superior vena cava syndrome

Unilateral or bilateral jugular vein or sigmoid sinus obstruction

Hyperviscosity syndromes

Masson’s vegetant intravascular hemangioendothelioma:

An uncommon, usually benign lesion that may rarely involve the neuraxis (including intracranial occurrence).
Not definitely neoplastic.
Organizing thrombi develop endothelialized projections into the vessel lumen.
Must be distinguished from other conditions such as angiosarcoma

Chiari I malformation (CIM)

May produce findings similar to PTC.

6% of PTC patients have significant tonsillar ectopia,

5% of PTC patients with CIM have papilledema

Infection (CSF will be abnormal in most of these)

Encephalitis

Arachnoiditis

Meningitis (especially basal meningitis or granulomatous infections, e.g. syphilitic meningitis, chronic cryptococcal meningitis),

Chronic brucellosis

Inflammatory conditions

Neurosarcoidosis

Vasculitis

Behçet’s syndrome

Metabolic conditions

Lead poisoning

Pseudopapilledema (anomalous elevation of the optic nerve head) associated with hyperopia and drusen.

Drusen: Small yellow deposits of fatty proteins (lipids) that accumulate under the retina

Retinal venous pulsations are usually present.

Especially deceptive when a patient with migraines has pseudopapilledema

Treat the H/A

Malignant hypertension

May produce H/A & bilateral optic disc edema, which can be indistinguishable from papilledema.

May also produce hypertensive encephalopathy.

Check BP in all PTC suspects

Meningeal carcinomatosis

Guillain-Barré syndrome

CSF protein is usually elevated 12. following head trauma

Reference

Antona 2021

Norager 2021