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Evaluation of a Patient with Suspected IIH

Once you understand the signs and symptoms of IIH, familiarizing yourself with the diagnostic criteria is helpful in the evaluation of a suspected patient.  

Once you understand the signs and symptoms that patients may experience with idiopathic intracranial hypertension (IIH), familiarizing yourself with the diagnostic criteria is helpful in the evaluation of a suspected patient.

Known as the modified Dandy criteria, the diagnostic criteria for IIH was revised in 1985, from its original version in the 1930s. Four fundamental features are required to establish the diagnosis of IIH:

  1. Symptoms consistent with increased intracranial pressure: headaches, vomiting, and nausea. Visual signs and symptoms such as blurriness, transient obscurations of vision, and papilledema.
  2. Normal neurological exam with the exception of unilateral or bilateral cranial VI nerve paresis.
  3. Elevated opening pressure on lumbar puncture (greater than 250 mm) and normal analysis of cerebrospinal fluid.
  4. Normal imaging of the brain1

Increased intracranial pressure can manifest in an array of symptoms from mild to severe. Headache is the most common complaint in one with IIH. This disabling symptom is nonspecific, highly subjective and conversely, patients without headache may have increased intracranial pressure. Other common complaints associated with an increased intracranial pressure are: nausea, vomiting, and visual complaints. A complete neurological exam is imperative to formulate a differential diagnosis.

The most common visual disturbance is blurring peripheral vision, due to the peripheral compression of the optic nerve. Transient obscurations of vision occur when a patient experiences spots or blurriness with a change in position, such as bending down to pick up an object. This occurs as elevated intracranial pressure is temporarily transferred to the optic disc. Papilledema – swelling of the optic nerve that carries visual signals from the eye to the brain – is not a requisite for diagnosis. Papilledema can be suspected by history alone as swelling of the optic nerve persists, vision worsens, and can progress to blindness, which can be permanent. The ability to see papilledema can be challenging and may need a specialist (such as a neuro-ophthalmologist) to appreciate. Peripheral vision blurriness progressing to blindness is an emergency requiring immediate lumbar puncture and transfer to a facility in which specialty services can be provided.

A lumbar puncture is a minor diagnostic procedure that has associated complications that range from a more common, less severe risk such as headache to much more rare, but more serious risks such as meningitis. With proper technique and thorough consent for this procedure, these complications can be minimized. Ideally, the patient should be positioned in lateral decubitus, as that position minimizes a falsely elevated opening pressure. During a lumbar puncture, if the patient is in an upright position, valsalvas or coughs, it can falsely elevate the opening pressure measurement. A reading of greater than 250 mm is considered elevated.

It is recommended that at least 10 mL of CSF be withdrawn for a full analysis to be conducted. Specific testing of cerebrospinal fluid can include: microbiology, biochemistry, xanthochromia, oligoclonal bands, cytology, cytospin, viral PCR, angiotensin-converting enzyme, and lactate. Each component must result in a normal finding or another diagnosis should be investigated 2.

Though the true definition of IIH is without any neuroimaging findings (idiopathic), with improved technology, distinct findings can be suspicious of increased intracranial pressures.

Structural Magnetic Resonance Imaging (MRI) can evaluate the anatomy and physiology of the brain. It is helpful to detect abnormalities that are associated with increased intracranial pressure such as reduction of the pituitary gland size “empty sella”, “slit” ventricles, distention of the optic nerve sheath, and unilateral or bilateral venous sinus stenosis3. Optical coherence tomography and its applications are being considered to diagnose papilledema3.

Other well-documented signs and symptoms of IIH include radicular pain, sixth nerve palsy VI, and pulse synchronous tinnitus4. Radicular pain is hypothesized to be an effect of increased cerebrospinal fluid pressure, compressing nerves in the arms and legs and causing the sensation of pins and needles. Sixth nerve palsy is the weakening of the lateral rectus muscle of the eye and can lead to double vision. Cranial nerve VI makes a sharp turn as it travels along the clivus (the bony part of the cranium at the base of the skull), it is easily compressed especially in light of increased intracranial pressure. Pulse synchronous tinnitus is the humming, whooshing, whistling, or marching noise that can be heard in one or both ears that are in sync with the patient’s pulse. This symptom is associated with dural venous sinus stenosis in close proximity to the ear. These findings can be detected with a thorough history and physical examination.

Keeping in mind that the classic patient for IIH is a female in her fertility years who is overweight or obese, however, this condition can also occur in men. Symptoms may fluctuate with rapid weight or with changes in medications that are associated with IIH. In rare cases, a patient can still have elevated intracranial pressures without papilledema and normal opening pressure on a lumbar puncture. If you believe one may have IIH despite meeting the above criteria, it is best to initiate work up in an expeditious manner and timely referral to the appropriate specialists.

  1. Friedman D, Jacobson D. Diagnostic criteria for idiopathic intracranial hypertension. Neurology. November 26, 2002;59(10):1492-1495.
  2. Doherty C, Forbes R. Diagnostic Lumbar Puncture. Ulster Med J. March 6, 2014;83(2):93-102.
  3. Moreno-Ajona D, McHugh J, Hoffman J. An Update On Imaging of Idiopathic Intracranial Hypertension. Front Neuro. June 10, 2020;11. https://www.frontiersin.org/articles/10.3389/fneur.2020.00453/full
  4. Ball A, Clarke C. Idiopathic intracranial hypertension. The Lancet Neurology. May 2006;5(5):433-442.

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