Idiopathic Intracranial Hypertension (IIH) Flashcards

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1
Q

What condition is marked by an elevated intracranial pressure (ICP) though there are no central nervous system issues, structural abnormalities, or obstructive hydrocephalus, but thought to instead be secondary to an impairment to CSF absorption at the arachnoid granulations?

A

Idiopathic intracranial hypertension (IIH), also known as pseudotumor cerebri, is a condition of elevated intracranial pressure (ICP) without structural abnormalities or hydrocephalus, caused by impaired CSF absorption at the arachnoid granulations.

The same underlying issue is seen with normal pressure hydrocephalus.

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2
Q

What is IIH?

A

Idiopathic intracranial hypertension (IIH), often referred to as pseudotumor cerebri or benign intracranial hypertension, is a condition of unknown etiology that manifests with chronically elevated intracranial pressure (ICP). It predominantly affects obese women, especially such who have gained significant weight over a short period of time, but certain drugs (growth hormones, tetracyclines, excessive vitamin A) are also associated with the condition. The most common symptoms are diffuse headaches, although various visual symptoms and pulsatile tinnitus are also common. Ophthalmologic examination is crucial for confirming the diagnosis and usually reveals bilateral papilledema and possibly loss of vision. MRI is often done to rule out other causes of increased ICP. Lumbar puncture typically shows an elevated opening pressure. Acetazolamide is the first-line therapy, whereas surgery is only used as a last resort. Even with treatment, the condition often worsens over the course of months to years, and permanent symptoms are common.

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3
Q

What are the major risk factors for IIH?

A
  • Women of childbearing age (most common).
  • Obesity or recent weight gain.
  • Medications: retinoids (vitamin A or isotretinoin), tetracyclines (minocycline or doxycycline), growth hormone, danazol.
  • Underlying conditions: Polycystic ovary syndrome (PCOS).
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4
Q

What is the pathophysiology of IIH?

A

Poor CSF absorption by the arachnoid granulations, leading to elevated ICP and increased pressure in the subarachnoid space.

A mismatch between production and resorption of CSF (cause unknown) → ↑ ICP → damage to structures of the CNS and especially to the optical nerve fibers

Orthograde axoplasmic flow stasis at the optic nerve head leads to bilateral papilledema.

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5
Q

What is the classic demographic for IIH?

A
  • Female.
  • Age: 15–44 years (childbearing age).
  • Obese or recent weight gain.
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6
Q

What are the classic symptoms of IIH?

A
  • Headaches: Worse in the morning, marked improvement when standing.
  • Nausea and pulsatile tinnitus.
  • Transient visual obscurations and temporary vision loss due to expansion of the physiological blind spot.
  • Papilledema.
  • Cranial nerve VI palsy (abducens nerve) causing impaired lateral gaze and/or diplopia.
  • Enlarged blind spots.
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7
Q

What findings on fundoscopic exam are associated with IIH?

A
  • Papilledema: Swelling of the optic discs.
  • Enlarged blind spots.
  • Possible hemorrhages or exudates in severe cases.
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8
Q

What is the order of diagnostic steps for IIH?

A
  1. Physical exam: Identify bilateral papilledema and visual symptoms.
  2. Vision testing: Fundoscopy and perimetry.
  3. Neuroimaging: MRI/MRV to rule out structural abnormalities or thrombosis.
  4. Lumbar puncture: Confirm elevated ICP.
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9
Q

What is the recommended diagnostic workup for IIH?

A
  1. Physical examination: Evaluate for papilledema and cranial nerve VI palsy.
  2. Vision assessment: Fundoscopy and perimetry (visual field testing).
  3. Perform imaging with either CT or MRI to rule out masses (with possible MRV to rule out venous sinus thrombosis).
  4. Last step is then to perform a Lumbar puncture (LP) to assess for an elevated opening pressure (>25 cm H₂O) with normal CSF composition.
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10
Q

What makes an LP “safe” when preformed for IIH?

A

In communicating hydrocephalus (e.g., in IIH), there is no pressure difference between the ventricles and subarachnoid space. Therefore, a decrease in intracranial pressure poses little risk of herniation. Unlike in meningitis, papilledema and other signs of increased intracranial pressure are not a contraindication for LP in IIH.

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11
Q

How is IIH managed nonpharmacologically?

A
  • Weight reduction (key for obese patients).
  • Avoid medications that exacerbate IIH (e.g., retinoids, tetracyclines).
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12
Q

What are the first-line medications for IIH?

A
  • Acetazolamide: Reduces CSF production by inhibiting carbonic anhydrase.
  • Topiramate: Alternative that also provides weight-loss benefits.
  • Steroids are used for acute symptom management, such as rapidly progressing vision loss.
  • Lumbar punctures (done acutely as well) performed serially for routine management.

** These interventions are provided following lifestyle, and medical management **

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13
Q

What are the surgical options for IIH, and when are they used?

A
  • Optic nerve sheath fenestration: Performed if progressive vision loss occurs despite medical therapy.
  • CSF shunting: For refractory cases to divert CSF and lower ICP.
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14
Q

What imaging findings are seen in IIH?

A
  • MRI: Normal brain parenchyma with small or normal ventricles.
  • MRV: Rules out venous sinus thrombosis.
  • Flattening of the posterior globe and empty sella are additional findings.
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15
Q

What complications can arise from untreated IIH?

A
  • Permanent vision loss due to chronic optic nerve damage.
  • Persistent headaches and impaired quality of life.
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16
Q

What is the role of lumbar puncture in IIH?

A
  • Diagnostic: Elevated opening pressure (>25 cm H₂O) confirms increased ICP.
  • Therapeutic: Temporarily reduces ICP and relieves symptoms.
17
Q

What are the clinical indications for optic nerve sheath fenestration or CSF shunting in IIH?

A

Performed when progressive vision loss occurs despite medical therapy.

18
Q

What are the high-yield associations with IIH?

A
  • Obesity and recent weight gain.
  • Medications: Tetracyclines, retinoids, growth hormone, danazol.
  • Polycystic ovary syndrome (PCOS).
  • Cranial nerve VI palsy.
  • Normal neuroimaging with small or normal ventricles.