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Spontaneous intracranial hypotension may be more than just a postural headache
Abstract & Commentary
By Dara G. Jamieson, MD, Associate Professor, Clinical Neurology, Weill Medical College, Cornell University. Dr. Jamieson is a consultant for Boehringer Ingelheim and Merck, and is on the speaker's bureau for Boehringer Ingelheim, Merck, Ortho-McNeil, and Pfizer.
Synopsis: Although spontaneous intracranial hypotension (SIH) generally causes a benign, self-limited, postural headache, subdural hematomas may occur in SIH with serious sequelae.
Source: Lai TH, et al. Subdural haematoma in patients with spontaneous intracranial hypotension. Cephalalgia. 2007:27:133-138.
Spontaneous intracranial hypotension (SIH) causes the new onset of a daily persistent headache with the distinctive feature of prominent increase of pain while upright and marked improvement in pain while recumbent. This striking exacerbation of pain with sitting or standing is distinct from the worsening of headache pain with head movement that migraine patients describe as a peripheral sensitization phenomenon. Despite its name, SIH may not always be truly spontaneous as minor trauma, especially in susceptible individuals, can cause the development of cerebrospinal fluid leakage with decreased intracranial pressure. The headache is due to the downward movement of the brain in the erect position with traction on pain-sensitive structures, including cerebral veins and sinuses. An MRI of the brain with contrast may be normal, but it can show meningeal enhancement, low-hanging cerebellar tonsils, or decreased ventricular and cisternal size. Rarely, subdural fluid collections, hematomas and hygromas, are seen. MRI of the spine, myelography, and cisternography, as well as low opening pressure on lumbar puncture, may also be used to diagnose SIH and identify the location of the dural tear. The treatment of SIH is generally conservative management (hydration, caffeine, pain medication, time) or epidural blood patching. Although patients are often quite disabled over the short-term by the severe postural head pain, the long-term prognosis is generally favorable with resolution of the headache in days to weeks.
The radiological features and time-course of SIH is not well documented in this relatively rare cause of headache. Lai et al reviewed records of a tertiary medical center in Taiwan and found 40 patients (18 women, 22 men, age ranging from 24-78 years) with SIH. They all had at least one MRI study, with 8 patients having a subdural hematoma (SDH) and 9 patients having nonhemorrhagic subdural fluid collections. Of the 8 patients with SDHs, 6 patients had bilateral SDHs and the other 2 had unilateral SDH with contralateral nonhemorrhagic subdural fluid collections. Two patients who had nonhemorrhagic subdural fluid collections converted the collections to hematomas on repeat MRIs. The presence of a subdural fluid collection did not correlate with age or headache intensity. However, having a SDH was more likely to be associated with neurological deficits and headache recurrence during the disease course. A patient with SDH was more likely to be a man. Although SIH is generally considered to be a benign condition, it can result in change in level of consciousness and focal neurological symptoms, especially when associated with a SDH. One patient had bilateral hand numbness that resolved after the SDH was evacuated. Another patient with a SDH became unconscious with transtentorial herniation, requiring blood patch, hematoma evacuation, and suboccipital decompression. Only 2 of the 8 SDH patients required surgical intervention and the 3 patients with midline shift > 5 mm had total recovery without surgery. Overall there was good symptomatic recovery at 3 months in all 3 groups: no SDH or nonhemorrhagic subdural collection. Mild headaches persisted in one patient without a subdural fluid collection, but the patient with transtentorial herniation was severely disabled. The presence of a SDH increased the chance of neurological deficits and recurrence of severe headaches.
This paper highlights a rare but dramatic cause of new onset headache, which may also be associated with a subdural fluid collection. Etiologies of the SDH in SIH include traction on bridging veins, development of new dural vessels in delayed SDH, or evolution of nonhemorrhagic to hemorrhagic subdural collections. The pathogenesis of the SDH may be variable, especially since a diagnostic lumbar puncture could cause a delayed SDH. The authors of this relatively large series of patients conclude that while most patients with SIH have a benign headache, patients with both SIH and SDH are not without risk. Headaches caused by SIH are probably under recognized and SDH may not be found in patients with SIH who do not undergo multiple imaging studies over time. If a patient with a headache characteristic of SIH does not improve consistently over days to weeks, or if the patient has a worsening of the headache, especially if accompanied by focal neurological symptoms or signs, then the patient may have an associated SDH.