How Can Neurologists Diagnose Spontaneous Intracranial Hypotension?
Imaging results may be negative, but risk factors and symptoms can make the diagnosis more certain.
Neurology Reviews. 2018 September;26(9):20
SAN FRANCISCO—Spontaneous intracranial hypotension (SIH) sometimes may go undiagnosed, partly because the disorder is uncommon. But patients will receive the care that they need if neurologists, particularly headache specialists, understand how to identify the disorder.
Misconceptions About SIH
The name of the disorder can be misleading, said Deborah I. Friedman, MD, at the 60th Annual Scientific Meeting of the American Headache Society. SIH is not always spontaneous; it often has an antecedent cause. Furthermore, the main problem is not intracranial, it is a leak in the spinal column, most often in the low cervical or thoracic zone. Finally, CSF pressure is usually normal in these patients, said Dr. Friedman, Chief of the Division of Headache Medicine, Professor of Neurology, and Professor of Ophthalmology at the University of Texas Southwestern Medical Center in Dallas.
Deborah I. Friedman, MD
SIH is considered a rare disorder, and its published annual incidence is five cases per 100,000 people. But this prevalence may be a gross underestimate that results from the absence of an ICD-9 or ICD-10 code for the condition, according to Dr. Friedman.
SIH is “much more common than we think,” she asserted. “These people are out there. They are in your offices. I can guarantee you, there are patients you have been seeing for years in your practice that have [SIH]. I have missed it. I bet you have, too.”
Guidelines for Identifying SIH
Dr. Friedman offered advice from the perspective of a headache specialist to guide the diagnosis of SIH. “Most of the literature that is out there, and it is good literature, was not written by headache medicine specialists, it was written by famous and prominent neurosurgeons and neuroradiologists. But the people we see are not necessarily the people they see,” Dr. Friedman explained.
SIH can be challenging to diagnose because of its myriad presentations. “You need to be a detective,” said Dr. Friedman. The questions to ask center around whether the headache has postural, end-of-the-day, and Valsalva components. Joint hypermobility may provide another clue.
Headache is the most common symptom of SIH and the reason that patients with the disorder seek a headache specialist. A neurologist should consider the diagnosis in a patient with a new daily persistent headache or in a patient with a diagnosis of chronic migraine for whom no medication has worked. “The people who come in with a huge list of medications they have tried, and nothing works? That is unusual for migraine. Usually something works for migraine,” said Dr. Friedman.
SIH can result in a headache with an onset as sudden as that of thunderclap headache, but this characteristic is not necessary. The most common location of pain is posterior, but the pain can be centered anywhere in the head or face. Bilateral pain is more common than unilateral pain.
The most typical headache is orthostatic or worsens at the end of the day. The longer a patient has SIH, the less likely that it will have a postural component. Most 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, or sexual activity. Caffeine often works well for people with SIH. A neurologist should ask the patient about these issues, said Dr. Friedman.
Besides headache, other common symptoms of SIH include tinnitus, abnormal hearing (eg, hearing things as though one is underwater), neck pain, imbalance, pain between the shoulder blades, and blurred or double vision.
Typical risk factors 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; and valvular heart disease. Joint hypermobility is widespread among patients with SIH. These patients often enjoy yoga and were exceptionally flexible as children. Many participated in gymnastics, ballet, or cheerleading as children.