VOLUME 24 • NUMBER 18 September 15, 2002
A BIWEEKLY PUBLICATION FOR CLINICAL NEUROSURGICAL CONTINUING MEDICAL EDUCATION
Spontaneous Intracranial Hypotension Meic H. Schmidt, M.D., and Devin K. Binder, M.D., Ph.D. Learning Objectives: After reading this article, the participant should be able to: 1. Identify the clinical syndrome of spontaneous intracranial hypotension. 2. Describe the diagnostic workup and imaging findings in patients with spontaneous intracranial hypotension. 3. Describe the guidelines and treatment options used in the management of spontaneous intracranial hypotension. Spontaneous intracranial hypotension (SIH) is a wellrecognized clinical syndrome that probably is underdiagnosed as a cause of headaches. Leakage of spinal cerebrospinal fluid (CSF) is the most common origin of SIH but also the most difficult cause to diagnose. Other etiologies of SIH, such as spontaneous CSF rhinorrhea or otorrhea, are much less common—and also easier to recognize. This article reviews the diagnosis and treatment of SIH secondary to spontaneous spinal CSF leakage. Post-lumbar puncture headaches have been described since Quincke introduced the concept of lumbar puncture in 1891. The German neurologist Schaltenbrand first described a group of patients with symptoms resembling post-lumbar puncture headache who had spontaneously low or even negative CSF pressures and accompanying orthostatic headaches. He termed this condition primary spontaneous intracranial hypotension, or “essential aliquorrhea.” Subsequent investigators further defined this syndrome as intracranial hypotension, or “hypoliquorrhea.” Originally it was thought that the hypo- or aliquorrhea resulted from either decreased production or increased reabsorption of CSF. In early cases, isotope cisternography was used to demonstrate normal CSF flow and rapid appearance of isotope in the urinary bladder. These factors are inconsistent with decreased production but consistent with either hyperabsorption or cryptic CSF leakage. Even as
recently as the early 1990s, some investigators believed that hyperabsorption of CSF was responsible for intracranial hypotension, despite reports of patients with spinal CSF leaks that closed after local treatment. In 1992, Rando and Fishman reported two cases of intracranial hypotension in which radionuclide cisternography demonstrated localized CSF leaks. They hypothesized that in these cases, the CSF leak was due to the spontaneous rupture of a spinal arachnoid (Tarlov) cyst. Based on this report and on subsequent series, it is now thought that spontaneous spinal CSF leaks are the most common cause of SIH. The exact etiology of spontaneous spinal CSF leaks is unknown, but they probably are caused by weakness of the meninges surrounding the spinal cord. There have been case reports of spontaneous CSF leaks associated with generalized connective tissue disorders. Meningeal diverticula and SIH have been described in association with Marfan syndrome, and meningeal diverticula also have been described in autosomal dominant polycystic kidney disease, neurofibromatosis type 1, and Lehman syndrome. The presence of structural dural weakness or meningeal diverticula may allow CSF to leak into the extradural space, particularly after mild trauma. Mild trauma can precipitate CSF leakage with these predisposing factors, and often it is associated with onset of SIH. Other possible causes to consider are CSF leaks from bone spurs piercing the dura or iatrogenic causes (e.g., after thoracic or spinal surgery).
Dr. Schmidt is Assistant Professor of Neurosurgery, University of Utah Medical Center, 30 N. 1900 East, Suite 3B-409, Salt Lake City, UT 84132-2303, E-mail:
[email protected]; and Dr. Binder is Senior Resident of Neurosurgery, Department of Neurological Surgery, University of California, San Francisco, CA.
Clinical Manifestations
The authors have disclosed that they have no significant relationships with or financial interests in any commercial organizations pertaining to this educational activity.
Spontaneous intracranial hypotension often is characterized by orthostatic headache that worsens with upright Category: Spine Key Words: Headache, Cerebrospinal fluid, Orthostatic, Spinal cere-
brospinal fluid leak
posture and improves when recumbent. However, in the presence of subdural effusions or hematoma, the headache may be constant and lack postural features. In most cases, onset of the headache is gradual or subacute. Some patients may present with “thunderclap” headache that is similar to headaches secondary to aneurysmal subarachnoid hemorrhage. The headache may be holocranial or localized to the frontal or occipital regions. It probably is caused by CSF volume loss and subsequent traction on the pain-sensitive intracranial dura due to downward brain displacement. Other symptoms that are associated with the headache can be diverse and may include neck pain or stiffness, nausea, vomiting, horizontal diplopia, dizziness, hearing and visual changes, phonophobia, and photophobia. Horizontal diplopia, hearing changes, and vertigo may be caused by traction of the abducens, cochlear, and vestibular nerves. Facial numbness or pain may
be due to traction of the trigeminal nerve, transient visual obscurations by traction of the optic apparatus, and galactorrhea by traction of the pituitary stalk. In rare instances, brain sagging may lead to signs of transtentorial herniation with stupor.
Diagnosis Neuroradiologic evaluation is crucial in the evaluation and management of SIH, both for the initial diagnosis and for accurate localization of the site of the CSF leak. In the early 1990s, advances in MRI dramatically facilitated the diagnosis of intracranial hypotension. The main imaging findings of SIH on CT and MRI scans reflect CSF volume loss and compensatory increased venous blood volume. These findings include descent of the brain into the posterior fossa, pachymeningeal enhancement, and bilateral subdural hygromas (Fig. 1). Other features include enlargement
Figure 1. A: CT scan demonstrating bilateral subdural fluid collection in a patient with spontaneous intracranial hypotension (SIH). B: T1-weighted MRI scan in the same patient demonstrating downward displacement of the midbrain, pons, and optic chiasm (arrow). C: Coronal gadolinium contrast-enhanced image showing the diffuse dural enhancement associated with SIH (arrows) and a right subdural effusion (arrowheads). (Reprinted with permission from Binder DK, et al: Intrathecal saline infusion in the treatment of obtundation associated with spontaneous intracranial hypotension: technical case report. Neurosurgery 51: 830, 2002.) EDITOR: Ali F. Krisht, M.D.* University of Arkansas for Medical Sciences PRODUCTION ASSISTANT: Ronalda Williams EDITORIAL BOARD: Ossama Al-Mefty, M.D. Evandro De Oliveira, M.D. Curtis A. Dickman, M.D. Rudolph Fahlbusch, M.D. John Fox, M.D. Allan Friedman, M.D. Douglas Kondziolka, M.D. Mark Linskey, M.D. Tom Origitano, M.D. Glenn Pait, M.D. Kalmon Post, M.D. Chandra Sen, M.D. Robert Solomon, M.D. Martin Weiss, M.D. Gazi Yas¸argil, M.D. * Dr. Krisht has disclosed that he has no significant relationships with or financial interests in any commercial organizations pertaining to this educational activity.
The continuing education activity in Contemporary Neurosurgery is intended for neurosurgeons, neurologists, neuroradiologists, and neuropathologists.
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of the dural venous sinuses and pituitary gland, and chiasmatic drooping on the dorsum sellae. Pachymeningeal enhancement following gadolinium administration occurs in 90% or more of patients with intracranial hypotension. It is thought to result from dural venous engorgement secondary to increased intracranial blood volume following CSF volume depletion, according to the MonroKellie rule (which defines the cranial cavity as a closed, rigid compartment and states that any change in the amount of intracranial blood can occur only if it is displaced or replaced by CSF). A similar mechanism involving venous hyperemia may account for enlargement of the pituitary gland. Meningeal biopsies that have been obtained in the past have demonstrated thin-walled dilated blood vessels without inflammation. However, meningeal biopsy is not necessary for diagnosis. Another characteristic of SIH is descent of the brain into the posterior fossa, also called brain sagging or pseudoChiari malformation. Imaging features include effacement of basal cisterns, flattening of the pons against the clivus, and hindbrain herniation with tonsillar ectopia (see Fig. 1). Tonsillar displacement into the spinal canal may prompt the diagnosis of Chiari I malformation; some patients with SIH, therefore, have undergone unnecessary suboccipital decompressive surgery. Finally, subdural fluid collections commonly are seen in patients with SIH. Subdural hematomas are thought to result when bridging veins are torn as a result of downward brain displacement. According to the Monro-Kellie rule, subdural hygromas may constitute a compensatory increase in the volume of the subdural space. Evaluation of CSF by lumbar puncture is unnecessary for the diagnosis of SIH. Indeed, lumbar puncture may create another leak and aggravate the syndrome. Typically, opening pressure of less than 60 mm H2O is documented, and in some cases, CSF can be obtained only via Valsalva maneuver or by aspiration. Examination of the CSF variably demonstrates pleocytosis, elevated protein, and xanthochromia. In some cases, this has led to the erroneous diagnosis of aseptic meningitis or encephalitis, particularly if a contrastenhanced MRI scan was misinterpreted or omitted.
leaks are found at the cervicothoracic junction or in the upper thoracic spine, areas that can be difficult to image. Radionuclide cisternography has been used to evaluate spinal CSF leaks; it is less sensitive than CT myelography, however, and it has poorer spatial resolution. In general, radionuclide cisternography is more useful in patients with cranial CSF leaks.
Treatment The headache that accompanies SIH can resolve without treatment. Occasionally, a prolonged period of bed rest is required (3 to 5 days). With intractable, persistent headache or other symptoms of SIH, the preferred treatment is an epidural blood patch. A large-volume blood patch (>20 mL) is recommended, because smaller volume may not cover adequate epidural territory. Because the most common site of leaks is the cervicothoracic region, the patient should be placed in a reverse Trendelenburg position, with the head lowered about 30 degrees, for a minimum of 10 minutes after the large-volume patch has been administered. Relief of symptoms often is immediate, due to thecal compression and increased CSF pressure. After successful administration of a blood patch, the clinical and imaging findings of SIH may resolve. Long-term effectiveness presumably relates to dural tamponade or fibrosis that scars over the site of the leak. Occasionally, several largevolume blood patches are necessary for permanent benefit. The initial blood patch usually is placed in the lumbar spine, regardless of the site of the leak, because the blood is known to spread over many levels. If ineffective, a more directed patch can be administered following more precise localization of the site of the fistula. A direct blood patch can be placed under either fluoroscopic or CT guidance. Other techniques that have been used include epidural saline infusion and percutaneous fibrin glue injection. If all other measures fail, and the leak has been well localized by imaging studies, surgical repair of the leak can be attempted. This has been especially effective in the treatment of meningeal (Tarlov) cysts. Ligation of the diverticulum or packing of the epidural space with Gelfoam or fibrin glue has proved effective in individual cases. Cervical and thoracic disc/osteophyte complexes have been reported as structural causes of SIH; in such cases, removal of the spur and repair of the dural defect have resulted in resolution of symptoms. In some cases, SIH may not have a benign or indolent course. Several cases have been described in which a rapid or progressive decline in mental status was seen in patients with SIH. The obtundation or stupor that results presumably is related to brain sagging leading to diencephalic compression. In such cases of rapidly declining mental status, lumbar intrathecal saline infusion may be implemented to arrest or reverse impending transtentorial herniation. Thereafter, once the patient’s mental status has been stabilized, diagnostic and therapeutic maneuvers aimed at localizing and sealing the site of the leak can be performed.
Localization of the Site of Cerebrospinal Fluid Fistula The site of a CSF fistula can be difficult to find; in fact, sometimes such a fistula cannot be localized. The search often begins with fat-suppressed, fast spin echo MRI of the spine, which may demonstrate an extradural collection of CSF or a prominent perineural cyst. Supportive evidence for a spinal CSF leak includes CSF hygroma, epidural venous engorgement and dural enhancement, and paraspinous fluid collections behind C1-C2. However, spinal MRI often is not sensitive enough to detect the actual site of a CSF leak, although extrathecal CSF accumulations and meningeal diverticula are visible. Dynamic decubitus myelography followed by CT myelography currently is the study of choice for defining the exact location of spontaneous CSF leak. Computed tomographic myelography can demonstrate the site of extrathecal contrast accumulation or define anatomic abnormalities such as meningeal diverticula. Most
Summary Spontaneous intracranial hypotension is being recognized as a cause of orthostatic headache with increasing frequency. 3
Any patient with orthostatic headache, bilateral subdural fluid collections, and no clear history of trauma should be investigated with contrast-enhanced MRI. If imaging findings are consistent with SIH, further investigation for an occult spinal CSF leak should be undertaken. Recognition and correct diagnosis of this condition may make it possible to avoid inappropriate therapeutic maneuvers such as burr holes or suboccipital decompression. Finally, it is important for neurosurgeons to recognize that the course of SIH may not always be benign and that obtundation related to diencephalic compression may be reversible via intrathecal saline administration. Appropriate localization with contrast myelography and treatment via epidural blood patch of the spontaneous CSF leak can then be performed.
Binder DK, Schmidt MH: Spontaneous intracranial hypotension associated with transdural thoracic osteophyte reversed by primary dural repair. J Neurosurg 2002 (in press) Dillon WP, Fishman RA: Some lessons learned about the diagnosis and treatment of spontaneous intracranial hypotension. AJNR Am J Neuroradiol 19:1001, 1998 Fishman RA, Dillon WP: Dural enhancement and cerebral displacement secondary to intracranial hypotension. Neurology 43:609, 1993 Fishman RA, Dillon WP: Intracranial hypotension. J Neurosurg 86:165, 1997 Pleasure SJ, Abosch A, Friedman J, et al.: Spontaneous intracranial hypotension resulting in stupor caused by diencephalic compression. Neurology 50:1854, 1998 Quincke H: Die lumbarpunktion des hydrocephalus. Klin Wochenschr 28:929, 1891 Rando TA, Fishman RA: Spontaneous intracranial hypotension: report of two cases and review of the literature. Neurology 42:481, 1992 Schaltenbrand G: Normal and pathological physiology of the cerebrospinal fluid. Lancet 1:805, 1953 Schievink WI: Spontaneous spinal cerebrospinal fluid leaks: a review. Neurosurg Focus 9:1, 2000 Spelle L, Boulin A, Tainturier C, et al:: Neuroimaging features of spontaneous intracranial hypotension. Neuroradiology 43:622, 2001 Vishteh AG, Schievink WI, Baskin JJ, Sonntag VK: Cervical bone spur presenting with spontaneous intracranial hypotension: case report. J Neurosurg 89:483, 1998
Readings Binder DK, Dillon WP, Fishman RA, Schmidt MH: Intrathecal saline infusion in the treatment of obtundation associated with spontaneous intracranial hypotension: technical case report. Neurosurgery 51:830, 2002
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1.
6.
The syndrome of spontaneous intracranial hypotension resembles post-lumbar puncture headaches.
True or False?
True or False? 2.
7.
The most common cause of spontaneous intracranial hypotension is cerebrospinal fluid rhinorrhea.
8.
Spontaneous intracranial hypotension can be associated with connective tissue disorders such as Marfan syndrome.
9.
Postural headaches are always a feature of spontaneous intracranial hypotension.
Bed rest and use of an epidural blood patch frequently are unsuccessful as initial treatment. True or False?
True or False? 5.
The most common location of the cerebrospinal fluid leak is at the cervothoracic junction True or False?
True or False? 4.
MRI of the spine, CT myelography, and radionuclide cisternography can be used for localizing a spinal cerebrospinal fistula. True or False?
True or False? 3.
Gadolinium enhancement on MRI scans is thought secondary to compensatory venous engorgement.
10. Obtundation and severe stupor secondary to spontaneous intracranial hypotension can be treated with lumbar intrathecal saline solutions.
Pachymeningeal enhancement on gadolinium-enhanced MRI scans occurs in the minority of patients with spontaneous intracranial hypotension.
True or False?
True or False?
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