Spontaneous intracranial hypotension (SIH) is typically characterized by a postural headache due to low cerebrospinal fluid (CSF) pressure. Overall, SIH is uncommon with an estimated incidence of 5 per 100,000, but it is being increasingly recognized in the past few decades, likely due to the increased accessibility and resolution of magnetic resonance image (MRI) and other noninvasive imaging.1 It is believed that the most likely causes of low CSF pressure are spinal CSF leaks from weaknesses or diverticuli in the dura around nerve root sleeves, ruptured perineural cysts, ventral dural tears due to osteophytes, or CSF-venous fistulas.2 There may be an association with connective tissue disorders such as Marfan or Ehlers-Danlos syndrome that predispose patients to developing spontaneous CSF leaks,1,2 particularly when leak is due to nerve sheath dural defects. Postural headache is the hallmark of the disease, and the severity of the headache varies significantly. However, if the patient remains untreated, the positional nature of the headache does not always persist, making the diagnosis more cryptic. Brain MRI typically shows diffuse meningeal enhancement and “sagging” of the brain. An epidural blood patch is performed if conservative treatment is ineffective. We present a case of a patient with atypical presentation of postural headache and normal neuroimaging; the patient was treated successfully with epidural blood patch.
Written consent from the patient was obtained before publication of this report per our institutional policy.
A 56-year-old man presented with a 2-month history of headache to the pain medicine clinic. The headache was described as achy and bilateral in nature, starting in the frontal region and radiating to the occiput and neck. There was an associated fullness in the ears. There was no photophobia, nausea, numbness, or weakness. The headache came on after 2 hours of upright position. It improved approximately 15 minutes after lying down. There was no history of trauma. The patient had no medical history. He had normal blood pressure and a normal neurological and fundus examination. His brain MRI without contrast was normal. His total spine MRI without contrast did not show a CSF leak (Figure). The patient had been previously evaluated by a neurologist who had ordered the imaging studies. The patient was suspected to have SIH based on symptoms and was referred to the pain medicine clinic for consideration of an epidural blood patch. An epidural blood patch was performed at L4-5 under fluoroscopic guidance with 20 mL of autologous blood injected into the epidural space. The patient had immediate relief of his postural headache after the procedure. After 5 days, the headache recurred. However, the headache now came on after 8 hours of upright position. It was relieved by lying down. The patient was evaluated by a second neurologist, a headache specialist, who also suspected the patient to have SIH. The patient was referred back to the pain medicine clinic for consideration of a blood patch. A second epidural blood patch was performed, this time at L2-3 under fluoroscopic guidance with 20 mL of autologous blood injected into the epidural space. At follow-up, the patient noted resolution of his headache. Five months after the second epidural blood patch, the patient continued to be headache free.
The clinical presentation of patients with SIH revolves around symptoms of a positional headache, typically worsening with upright posture and improving when recumbent. Patients typically will have relief within 15–30 minutes of lying down. Other associated symptoms have been reported with SIH, including nausea, vomiting, posterior neck pain or stiffness, hearing disturbances, and subtle cognitive deficits.1 In patients who present with a constellation of symptoms concerning for SIH, brain MRI can support the diagnosis. Brain MRI without contrast is often performed for initial evaluation of headache, as in this case. However, one of the most common findings on brain MRI with contrast in SIH is diffuse, smooth, symmetric dural enhancement. Other findings include brain sagging, dilation of intracranial venous sinuses, and subdural fluid collections. If SIH is strongly suspected, spinal imaging can be ordered to check for direct evidence of CSF leak, typically via MRI or computed tomography (CT) myelogram. Regular spine MRI is noninvasive and can show evidence of large CSF leak but is not accurate at distinguishing actual site of CSF leak.3 If initial MRI results are not helpful, a CT myelogram with nonionic contrast or magnetic resonance myelogram with intrathecal gadolinium can be used. magnetic resonance myelogram may be particularly sensitive at detecting low-flow leaks that CT myelography cannot detect; however, magnetic resonance myelography should be reserved for only those patients who have a very high suspicion of spinal CSF leak and a nondiagnostic CT myelography, as intrathecal gadolinium is off-label.4 Cisternography is also a sensitive test to confirm a low-flow leak; however, it is limited in that it cannot anatomically localize the leak, thus not allowing for subsequent targeted therapy.5 CSF pressure measurement may also be ordered to establish the diagnosis of SIH. CSF pressure <6 cm H2O was initially believed to be a defining characteristic of SIH. However, it has become evident that many symptomatic patients with a known CSF leak will still have a normal CSF opening pressure and that low CSF pressure has a very low sensitivity for detecting the condition.6 Regardless, an opening pressure may be obtained concurrently when performing myelographic studies if one desires additional diagnostic information. Although generally safe, complications from myelographic studies can occur and include postdural puncture headache and rarely can lead to seizure, contrast reaction, spinal cord damage, hemorrhage, or infection.7
The case above is unusual because the patient was presumed to have SIH, and the decision was made to pursue epidural blood patch rather than additional diagnostic workup. Other than the primary complaint of postural headache, the patient had no associated symptoms, other clinical risk factors, and of particular note, no imaging findings on brain or spine MRI. Another unique feature of the case was the longer onset time of headache than is usual of most cases of SIH after upright posture. It has been noted that the positional nature of headache associated with SIH may be more variable with prolonged duration of untreated symptoms.8 The timing for relief of his symptoms after lying down was very typical. Indeed, the patient would not satisfy diagnostic criteria of the third edition of International Classification of Headache Disorders9 for headache due to SIH because of the lack of objective evidence of CSF leak or low pressure, but his positive response to epidural blood patches could arguably be considered diagnostic.8 Other options when treating this patient would have been to initially perform more costly or invasive imaging to look for other evidence of low CSF pressure or to determine an exact location of CSF leak. However, those tests and procedures may not be necessary since blind early lumbar epidural blood patch may have reasonable efficacy and low morbidity, as demonstrated by Berroir et al.10 In that study, 30 patients with diagnosis of SIH underwent blind lumbar epidural blood patch, and 23 were successfully treated with 1–2 blood patches. Of note, 11 of the 30 patients had normal brain MRI findings, and none had dedicated spinal imaging. Compared to the patients in that study, our patient may not have had as many clinical characteristics of SIH because he did not have many associated symptoms. Although our diagnosis was suspected but not definitive, epidural blood patching was attempted rather than seeking more objective data. Because the patient was seen by a specialist and deemed to have a reasonable suspicion of SIH, albeit with nonclassical symptoms, we think that this was an appropriate course of action. Further diagnostic testing may prolong the time before the patient can receive therapy, will increase health care expenditures, and expose the patient to complications and potential false positives11 from those procedures. If our patient did not respond to an epidural blood patch, more sensitive radiological testing, possibly for low-flow leaks such as those mentioned above, would certainly have been considered to solidify the diagnosis as well as provide the possibility of a targeted epidural blood patch as a treatment modality.
Thus, a subset of patients with SIH may present similarly to this case. Although there are studies on the efficacy of blind epidural blood patches10,12 and on epidural blood patch response stratified by brain imaging findings,13,14 more studies detailing therapeutic response to epidural blood patches in the setting of normal imaging would be helpful to further refine an effective treatment algorithm of this rare neurological condition.
Name: Nathan Swallow, MD.
Contribution: This author helped prepare the manuscript.
Name: Lisa V. Doan, MD.
Contribution: This author helped prepare the manuscript and conceive the study.
This manuscript was handled by: BobbieJean Sweitzer, MD, FACP.
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