SAN FRANCISCO – Spontaneous intracranial hypotension couldn’t have a more misleading moniker.
First of all, spontaneous intracranial hypotension (SIH) is not always spontaneous; often there is an antecedent causal event. Second, the main problem isn’t intracranial, it’s a leak in the spinal column, most often in the low cervical or thoracic zone. And cerebrospinal fluid (CSF) pressure is usually normal in these patients, Deborah I. Friedman, MD, said in the annual Seymour Solomon Award Lecture at the annual meeting of the American Headache Society.
Moreover, although SIH is usually labeled a rare disorder, with a published annual incidence of 5 cases per 100,000, that’s doubtless a gross underestimate stemming from the absence of an ICD-9 or -10 code for the condition, according to Dr. Friedman, chief of the division of headache medicine, professor of neurology, and professor of ophthalmology at the University of Texas Southwestern Medical Center, Dallas.
“[SIH is] much more common than we think,” she asserted. “These people are out there. They’re in your offices. I can guarantee you, there are patients you’ve been seeing for years in your practice that have [SIH]. I’ve missed it. I bet you have, too.”
She focused her award lecture on the diagnosis of SIH from the perspective of a headache specialist.
“Most of the literature that’s out there – and it is good literature – wasn’t written by headache medicine specialists, it was written by very famous and prominent neurosurgeons and neuroradiologists. But the people we see are not necessarily the people they see,” Dr. Friedman explained.
SIH can be a challenging diagnosis because of its myriad presentations.
“You need to be a detective,” she emphasized.
Headache is the most common symptom of SIH and the reason patients with the disorder seek out a headache specialist. It’s time to consider the diagnosis in a patient with a new daily persistent headache, or in the patient running around with a diagnosis of chronic migraine for which nothing works.
“The people who come in with a huge list of medications they’ve tried and nothing works? That’s unusual for migraine. Usually something works for migraine,” she observed.
The headache of SIH can be thunderclap in onset, although not necessarily so. The most common location is posterior, but the pain can be centered anywhere in the head or face. Bilateral pain is more common than unilateral.
The most typical headache pattern is one that’s orthostatic or gets worse at the end of the day. The longer a patient has SIH, though, the less likely that they’ll have a postural component. The majority of patients are awakened by their headache in the middle of the night. The headache is often exertional and usually worsens with Valsalva maneuvers, including coughing, sneezing, lifting, bending forward, straining, singing, and/or sexual activity. People with SIH often find that caffeine works very well for them. Ask nonleading questions about these issues, she suggested.
Besides headache, other common symptoms of SIH include tinnitus, abnormal hearing as if underwater, neck pain, imbalance, pain between the shoulder blades, and blurred or double vision.
Risk factors that are a tipoff include joint hypermobility, previous lumbar puncture, epidural or spinal anesthesia, known disc disease, or a personal or family history of retinal detachment at a young age, aneurysm, dissection, or valvular heart disease.
Joint hypermobility is really common in patients with SIH. These are often headache patients who enjoy yoga and were superflexible as children, participating in gymnastics, ballet, or cheerleading.
“We’re looking for Cirque du Soleil here, so you have to ask the Cirque du Soleil questions,” Dr. Friedman said.
On physical examination, she looks for joint hypermobility, makes sure that spontaneous retinal venous pulsations indicative of normal CSF pressure are present when she looks in the eyes, and puts the patient in 5 degrees of Trendelenburg position for 5-10 minutes to see if that improves the headache and other symptoms.
One of the first things Dr. Friedman does when she suspects the diagnosis is to send a patient to the recommendedof the Spinal CSF Leak Foundation. She asks them to take a look around the site and tell her if the descriptions sound like them.
There is broad agreement that the first-line diagnostic test is brain imaging via MRI with gadolinium enhancement. The diagnostic challenge posed by SIH is that the test is normal in 30% of affected patients.
At present there is no consensus as to the next move when the brain MRI is negative. Some favor CT with or without MR myelography, others a T2-weighted spine MRI. But despite a thorough search, no leak is found in about half of individuals with SIH.
Although Dr. Friedman focused on diagnosis, she turned briefly to treatment. She has found that conservative measures don’t work very well. A reasonable strategy, even if a leak site hasn’t been identified, is to treat with a high-volume epidural CT-guided targeted blood patch with fibrin sealant.
“It gives relief about a third of the time each time you do it,” according to Dr. Friedman.