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STUDY STRESSES NEED FOR AGGRESSIVE TREATMENT OF FULMINANT IDIOPATHIC INTRACRANIAL HYPERTENSION

For reasons unknown, certain people — often obese women of childbearing age — experience a disastrous increase in CSF pressure, causing papilledema and sometimes temporary or permanent vision loss. Management of the condition has been debatable and frequently disappointing.

In a Jan.16 study in Neurology (2007; 68:229–232), investigators reported on 16 cases of “fulminant idiopathic intracranial hypertension” (IIH), rare cases of acute onset and rapid progression. The authors consider fulminant IIH a medical emergency demanding aggressive treatment, including surgery in most cases.

“It is important not to delay surgery in those rare patients with acute symptoms and signs of IIH and rapidly progressive visual loss,” they wrote. “Only three patients who were hesitant about undergoing surgery, delayed the procedure by 10, 12, and 37 days after their neuro-ophthalmic evaluation. These three patients remain legally blind. All the patients who had major improvement of their visual function underwent surgery within a few hours to four days after neuro-ophthalmic evaluation.”

All patients reported dramatic improvement of headaches and vomiting following surgery. Fourteen patients had improved visual function after surgery, although eight patients remained legally blind.

IIH used to be known as “pseudotumor cerebri,” because the symptoms mimic those caused by the increased pressure of a brain tumor; another term is “benign intracranial hypertension,” but there is nothing “pseudo” or “benign” about the disorder, and today it is known primarily as IIH.

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Initial optic nerve appearance of four patients with fulminant idiopathic intracranial hypertension (right eye is on left; left eye is on right). Note the severe bilateral disk edema with dilated veins, numerous exudates, and peripapillary hemorrhages.

ETIOLOGY UNKNOWN

The authors of the Neurology article offered no new theories on the mysterious origin of IIH. One possible explanation is that the veins carrying blood from the brain to the heart drain excess spinal fluid and are blocked, causing CSF to accumulate in the brain. Another theory is that that tiny clots block the veins or arachnoid villi, or that excess weight compresses veins, which would explain why obese patients are predisposed to IIH. Other theories abound — regarding increased venous pressure, abnormal vitamin D metabolism, and endocrine abnormalities — but there is no clear consensus about the etiology.

While women are more prone to IIH than men by a ratio of at least two-to-one, and all 16 cases in the Neurology paper involved women who were overweight or obese, IIH sometimes affects men or women of normal weight.

A lumbar puncture to drain CSF and reduce the volume of CSF relieves intracranial pressure temporarily, according to the authors, and is often performed before surgery. Diuretics, especially acetazolamide, sometimes help as well.

Corticosteroids are sometimes administered to patients with fulminant IIH. Also, in cases with severe visual loss, slits can be created surgically in the optic nerve sheath to relieve the pressure — a procedure known as fenestration. In cases of IIH with intractable headache, a lumboperitoneal or ventriculoperitoneal shunt may be inserted to divert CSF from the lower brain or vertebral subarachnoid space to the abdomen.

VISUAL LOSS RELATED TO ISCHEMIC INJURY

While agreeing with the authors that fulminant IIH is uncommon, Steven L. Galetta, MD, professor of neurology and ophthalmology at the University of Pennsylvania School of Medicine, suspects that the apparently sudden onset may be superimposed on a chronic condition in many patients.

“Patients with IIH often show up and they probably have had optic nerve swelling for weeks or months,” he said. “We look at their optic nerves and can see that the swelling has been around for a while. Unfortunately, in some patients it hits a critical threshold and vision fails.”

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Dr. Steven L. Galetta: “You should consider surgery early in patients who have severe vision loss, especially if they dont respond in hours or days to a therapeutic trial of steroids or diuretics and intravenous corticosteroids.”

Dr. Galetta suspects that visual loss may be due to ischemic injury. “The nerves are under high pressure, which is transmitted to the optic nerves, causing them to swell,” he said. “As the swelling evolves, it compresses the vascular supply, which I think causes the acute deterioration — a vascular insult.”

That would explain why, after surgery to relieve pressure on the optic nerve in these fulminant cases, 50 percent of the patients remain legally blind, Dr. Galetta said. “Surgery doesn't allow some of these nerves to recover; there is nerve death. Even a heroic procedure may not affect vision in some who continue to have visual decline despite multiple interventions.”

Acute visual loss in IIH also may be caused by fluid or exudates in the retina or macula, Dr. Galetta said. “The optic nerve is under so much pressure that vessels may leak fluid,” he said. “In that case you may try steroids or diuretics to take fluid off the macula. Fenestration may or may not improve the swelling in the adjacent retina. It's important to have the patient examined by a neuro-ophthalmologist to determine if the visual loss is due to the nerve, or if there is a retinal component. You might try some other temporary measures if the visual loss is due to a retinal problem rather than an optic nerve problem.”

Nevertheless, immediate surgery sometimes may be the best course, according to Dr. Galetta. “I think there is a small subgroup that has severe visual loss, and you may want to consider surgery early in course,” he said. “We try medical therapy for hours or days — usually IV steroids and acetazolamide. If they respond, great. If not, then I would consider surgery — fenestration when the primary problem is visual; shunting when the primary problem is intractable headache.”

The lead author of the paper, Valerie Biousse, MD, of the departments of neurology and ophthalmology at Emory University, emphasized that visual loss is the most urgent danger facing patients with IIH.

“All patients with IIH, or disc edema from any cause of raised intracranial pressure, need an immediate comprehensive evaluation by an ophthalmologist,” she said. “Visual field tests need to be obtained regularly in these patients, since they may develop progressive and insidious visual loss. Treatment is mostly based on visual function and its progression.”

ARTICLE IN BRIEF

  • ✓ Investigators reported on 16 cases of “fulminant idiopathic intracranial hypertension” (IIH), adding that it is a medical emergency demanding aggressive treatment, including surgery in most cases.

REFERENCE

• Thambissety M, Levin PJ, Biousse V. Fulminant idiopathic intracranial hypertension. Neurology 2006; 68:229–232.