Diagnosis
The ophthalmic exam is a fundamental part of the diagnosis and management of intracranial hypertension. A direct funduscopic exam of the optic nerves should be performed at each visit to assess for the presence of edema. The degree of edema is graded using the Frisén scale, ranging from 0 (normal) to grade 5 (severe).24 Spontaneous venous pulsations (SVPs) at the optic nerve head have been evaluated as a marker for increased intracranial pressure. They have been documented in those with documented elevated intracranial pressure and absent in normal individuals. Thus decisions regarding workup and even treatment should not hinge upon the presence or absence of SVPs.
Humphrey or Goldmann visual fields are used to assess for visual field deficits seen with intracranial hypertension. Humphrey field testing is an automated test but unfortunately requires maintaining concentration. Some younger children can be assessed with Goldmann testing when they are unable to complete Humphrey field testing. An enlarged blind spot is the most common visual field defect. Peripheral constriction, paracentral scotoma, nasal field loss, and inferior arcuate defects are also seen.
B-scan ultrasound is used to detect calcified optic nerve head drusen, and thus differentiate true papilledema from pseudo-papilledema. However, in younger patients drusen may not yet contain calcification and is only detectable by fundus autofluorescence photography.
Neuroimaging should include MRI and MRV to rule out secondary causes. Subtle findings seen by the astute practitioner can include partially empty sella turcica, flattening of the posterior globe, dilation of the optic nerve sheath, slit-like ventricles, distal transverse sinus stenosis, anterior protrusion of the optic nerve head, and tortuosity of the optic nerve. The presence of one or more of these radiographic findings greatly increases the probability of having intracranial hypertension. However, the probability does not decrease in absence of these findings.
The final diagnostic component is the lumbar puncture. Proper positioning includes lateral decubitus with the legs and head extended at the time of measurement. Popular convention dictates the withdrawal of large CSF volumes to return the pressure to normal and help protect the vision. Johnston and colleagues achieved a normal pressure in a series of adult PIH patients through the removal of 15-25 ml of CSF. Using continuous pressure monitoring, they followed the time to return of their initial pressure, which averaged 82 minutes.25 Thus there is a questionable benefit to achieving normal pressure in these patients.
Studies on adult normative values for CSF opening pressure have consistently shown that the pressure must be in excess of 25 cm H20 to be considered abnormal.26-28 There has been no correlation found with the degree of obesity and opening pressure.26-28 Due to ethical considerations, there have not been many pediatric studies. Based on the few published works, some practitioners use >18 cm H20 for children under 8 years of age and >25 cm H20 for children 8 years or above or <8 in absence of optic nerve edema as abnormal.29
Two recent articles have questioned the use of these values.30,31 Avery et al. performed an analysis of patients receiving lumbar punctures as part of their workup for other conditions.30 They observed a mean opening pressure of 19.8 cm H20 and an upper limit of normal (i.e. the 90th percentile) of 28 cm H20. Lee et al. studied 44 patients who had a sedated lumbar puncture and found a mean of 20.3 cm H20.31 Both studies included patients with demyelinating and white matter disease in their normal patient sample (discussion is found in the online appendix for Avery et al.). In a separate analysis of the patients with demyelinating disease, Lee et al. found a mean opening pressure of 21.5 cm H20, which is higher than their total population mean (20.3 cm H20).31 Other published studies have shown patients with demyelinating disease have higher opening pressures.32-34 Thus inclusion of these patients in a normal population sample could result in a skewed average.
Outcome
Pain and permanent vision loss are the two major risks associated with intracranial hypertension, and both have an impact on the quality of life.41,42 Headache is typically the first symptom to resolve within the first few weeks following treatment initiation followed by papilledema over the subsequent 4-5 months. Post-pubertal status has been found to result in a worse visual outcome in one study.43 Another study found grade 3 or higher papilledema was a more predictive marker of visual deficits in the following resolution.44
Recurrence is estimated to occur in up to 20% of patients.45,46 Ko et al. followed a series of adult patients for recurrence, defined as the return of optic nerve edema.36 In those with recurrence, BMI was an average of 5.5% higher than at initial diagnosis. Those without recurrence had an average of 17.9% weight loss from diagnosis through the follow-up period. Interestingly, the average BMI in those without recurrence was greater than those with recurrence, suggesting weight gain is the major contributor, not the actual weight.
Once a patient’s intracranial hypertension has resolved, up to 68% report developing a new or chronic headache type that is different from their intracranial hypertension headache.47, 48 The most frequent diagnosis is episodic tension-type headache or migraine without aura. Fortunately, these headache types respond to the typical migraine prophylactic medications.
Treatment
Whenever possible, a multidisciplinary team should follow a patient with intracranial hypertension. This team should consist of at least a neurologist and an ophthalmologist. Neurosurgery, nutrition, physical therapy, psychology, hematology, and/or endocrinology should be included if warranted.
Post-pubertal patients often report recent weight gain over the 6-12 months preceding diagnosis. Numerous adult studies have shown improvements in symptoms and intracranial pressure through weight loss alone.35,36 In one of the initial studies, patients were treated with a low calorie and sodium rice diet.35 None received medications commonly used to treat intracranial hypertension. Weight loss ranged from 11-56 Kg, with a resolution of papilledema and the 2 symptomatic patients had complete symptom resolution.
Acetazolamide is considered the first-line treatment for intracranial hypertension. The primary method of action is carbonic anhydrase inhibition and resulting in decreased CSF production. In children doses of 25-100 mg/kg/day (maximum 2 gm/day) divided BID can be tolerated.37 Typical adolescent dosing is 1-2 g divided BID. Doses above 2 grams show questionable benefits at the risk of more side effects. Patients often complain of food having a metallic taste to it, especially carbonated beverages, often resulting in transient anorexia.
Furosemide works through diuresis resulting in reduced-sodium transport into the brain. The usual dose is 1-2 mg/kg/day divided BID/TID.37 Due to the diuretic effect, serum electrolytes must be monitored and potassium supplementation was given as needed. This is the main reason it is second-line therapy in pediatric patients. Studies do suggest a synergistic effect when used in conjunction with acetazolamide.38
Topiramate has weak carbonic anhydrase inhibition properties, making its mode of action similar to that of acetazolamide. An open-label treatment studies randomized cases with mild papilledema to treatment with either acetazolamide or topiramate. Using visual field grades to assess for improvement, they found statistically significant improvement amongst both groups suggesting it is a viable alternative.39
Corticosteroids used to be a mainstay of treatment for PIH, use has diminished with the discovery of other medication options with fewer side effects. The use of steroids with acetazolamide has been shown to improve the outcome in cases with severe visual deficits at the time of presentation. Dose recommendations are largely anecdotal and are typically the same used for other inflammatory neurologic disorders such as optic neuritis. A typical course involves intravenous methylprednisolone 20 mg/kg (maximum 1 gm) daily for 5 days followed by an oral taper.
Surgical intervention is reserved for patients in whom papilledema or pain persists despite maximum medical care, cannot tolerate medical therapy, or optic nerves are severely swollen at presentation with concern for permanent vision loss.
In general, optic nerve sheath fenestration (ONSF) is utilized to prevent further optic nerve injury by redirecting pressure away from the optic nerve head but does not effectively lower ICP by itself. Risks include ischemic optic neuropathy, transient blindness, pupillary mydriasis, and retrobulbar hemorrhage. Interestingly it has been demonstrated that unilateral fenestration can offer protection with improvements in the un-fenestrated eye. Caution should be used with ONSF in the acute presentation period, particularly in those with signs of ischemia, as the severe swelling and ischemia increase the risk of postoperative ischemic optic neuropathy.
CSF diversion is more effective in those with pain as the primary symptom, though it can be used to protect a patient’s vision in the acute period. There remains some debate even amongst neurosurgeons about whether lumbar or ventricular diversion is superior. Abubaker et al. compared outcomes for 25 patients shunted for management of their intracranial hypertension. They found a failure rate of 11% and 14% and a revision rate of 60% and 30% for LP and VP shunts respectively.40
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