A 56-year-old woman presented with severe orthostatic headache in association with nausea and vomiting. Lumbar puncture for the patient revealed significantly low cerebrospinal fluid pressure (CSF) and the clinical diagnosis of intracranial hypotension syndrome was made. An initial gadolinium-enhanced brain magnetic resonance imaging (MRI) disclosed diffuse meningeal enhancement as well as brain sagging. No definite CSF leakage was found using radionuclide cisternography. Her headaches abated with proper usage of analgesics, strict bed rest, and intravenous hydration. Follow-up neuroimaging studies showed partially resolved meningeal enhancement 2 months after treatment and complete resolution 6 months after treatment. The temporal changes found on MRI suggest that the pachymeningeal enhancement is reversible in patients with spontaneous intracranial hypotension. Moreover, proliferation of meninges is likely to be responsible for this type of delayed resolution phenomenon. (Chang Gung Med J 2003;26:293-8)

Key words:
intracranial hypotension, orthostatic headache, cerebrospinal fluid, magnetic resonance imaging.

CASE REPORT

A 56-year-old housewife suffered from severe headaches in December of 1999. At first, she experienced a dull head pain when she got up from her bed. The pain was mainly located at the vertex portion in association with tightness of the occipital and postnuchal areas. In particular, the headache was precipitated by erect posture and ameliorated immediately on lying flat. Dizziness, nausea, vomiting and tinnitus were also symptoms once the headaches became severe. She took acetaminophen and other non-steroid-antiinflammatory-drugs (NSAIDs) suggested by pharmacists and local clinicians for relief of the headaches. However, her headaches became incrementally more intense during the 3 weeks prior to admission and she was incapable of doing her housework. She denied any history of cranial or spinal trauma.
The patient was admitted to our ward in January of 2000 for investigation of the incapacitating headaches. The results of her complete physical examination were normal. On neurological examination, she was alert and oriented. Examination results of cranial nerve and eye fundus were unremarkable. No evidence of motor or sensory deficits were found. An elicitation of meningeal irritation sign was negative. An initial computed tomographic (CT) scan of the brain revealed slit-like ventricles and prominent meningeal enhancement. A CSF study revealed low opening CSF pressure (30 mm CSF), mild pleocytosis (WBC: 8 cells×109/L with mononuclear cells dominant), normal glucose level, and increased protein content (1150 mg/L). No subarachnoid block was found via the Queckenstedt test method. Cultures and cytological examination results of CSF were all negative. Accordingly, a clinical diagnosis of intracranial hypotension was established. Brain MRI with gadolinium enhancement showed bilateral subdural effusion as well as diffuse meningeal enhancement (Fig. 1A). In addition, downward displacements of the corpus callosum and cerebellar tonsil were disclosed on sagittal T1-weighted imaging (Fig. 1B). For further search of possible CSF leakage, a retrograde radionuclide cisternography was performed via a lumbar puncture using 10 湣i Technetium-99m-diethylamine-triamine-penta-acetic acid. The patient was in supine posture with scintigrams taken at 1, 2, 5, 24 and 48 hours, respectively. In addition to the slow ascent of the radioisotope along the spinal axis, non-visualization of radioactivity in the lateral ventricles was also found in serial scans. In the cerebral convexities, relative delayed and less than expected radioactivities were seen on the 24-hour scan. Of special note, no evidence of CSF leakage was identified.
Her headaches aggravated after the lumbar puncture and remained related to postural position. Since the IH syndrome has been mostly self-limited, conservative treatment with absolute bedrest, adequate hydration therapy, and NSAIDs were given. Two weeks after beginning treatment the orthostatic headaches gradually subsided and no more bed rest or medications were needed. A follow-up brain MRI at 2 months after treatment revealed diminished meningeal enhancement (Fig. 2A). In addition, evidence of reduced amounts of subdural effusion, diminished displacement of the corpus callosum, as well as restoration of cerebellar tonsils to a position just above the foramen magnum were also found (Fig. 2B). Six months after the episode, meningeal enhancement had fully resolved as shown on follow-up MRI (Fig. 3).

DISCUSSION

It is well known that headaches are one of the most common symptoms in patients with IH syndrome. The site of the headaches may be at the frontal, vertex, occipital regions, or the whole head. The characteristics are often varied, either throbbing or tension in nature, and are usually not relieved by analgesics alone.(5) Importantly, the head pain also varies in intensity, with associated clinical presentations such as dizziness, nausea, vomiting, and tinnitus.(8) Our patient presented with throbbing pain at the vertex in association with neck tightness, dizziness, nausea, and vomiting. In addition, her headaches were relieved quickly on recumbence. Therefore, a detailed search of causes underlying orthostatic headaches is warranted.
In IH syndrome, low CSF pressure in the absence of a spinal block is an important diagnostic clue. The opening CSF pressure in our patient was 30 mm, a level below normal ranges at the lumbar level. Nevertheless, low CSF pressure is not always present in patients with IH syndrome since Mokri et al. located spinal pressure between 65 and 140 mm CSF in five out of 26 IH patients.(7) On the other hand, augmentation of headaches with jugular compression, which actually increases the intracranial pressure, suggests that headaches in IH patients are not solely related to the intracranial pressure.(9) Grant and his colleague proposed that headache due to CSF leakage were caused by reduced CSF volume rather than lowered CSF pressure.(10) As a result of the reduction of CSF volume, venous dilation or distortion of the supporting structures of the brain may appear.(11) Accordingly, the source of headaches in patients with IH may come from painful venous dilatation or brain descent with traction of pain-sensitive structures.
Spontaneous IH syndrome, originally described by Schaltenbrand,(12) was thought to result from overt CSF absorption or occult CSF leakage from small dural tears. Rupture of perineural or epineural cyst, tearing of spinal meningeal diverticulum or nerve sheath all account for cryptic leakage of the spinal fluid.(3-5,13) Of particular importance, radionuclide cisternography or CT-myelogram can be helpful in detecting the CSF leakage sites.(3,14) In our patient the cisternography demonstrated no evidence of CSF leakage, however, slow isotope ascent and reduced hemispheric radionuclide activities were observed. These findings suggest either a possible CSF hyperabsorption state or an existing CSF leakage too small to be detected using the current studies.
Characteristic MRI findings of spontaneous IH syndrome include subdural fluid collections, brain sagging,(7) and diffuse pachymeningeal contrast enhancement.(6) Formation of subdural hematomas or hygromas have been frequently observed in patients with sustained IH syndrome.(4) These vascular complications may enrich clinical manifestations and contribute to, at least in part, the occurrence of postural headaches. Presumably, these are caused by ruptures of bridging veins when the brain pulls away from the dura as a result of decreased CSF volume.(4) In our patient, diminished amount of subdural effusion was evident after proper management and this substantiated the role of CSF volume. The descent of the brain has been described as inferior displacement of the optic chiasma and iter, flattening of the pons, effacement of the prepontine, superior and inferior cerebellar cisterns, and caudal displacement of the pons and cerebellar tonsils.(15) In some patients, the descent of the brain can be measured on the midsagittal plane of an MRI.(16) First reported in 1991, the characteristic MRI findings for patients with IH syndrome included diffuse, even, uninterrupted enhancement involving the pachymeninges with thickened dura on contrast-enhanced T1-weighted and slight hyperintense on T2-weighted imaging. The mechanism of meningeal enhancement may be due to inflammation of the pachymeninges secondary to reversible disturbance of the choroid plexus,(16) dural venous dilatation secondary to reduced CSF volume,(15) or fibrocollagenous proliferation of the leptomeninges.(17) Resolution of imaging abnormalities has been emphasized after proper treatment and used to be in accordance to clinical improvement.(4,7,16,18) In our patient, a follow-up MRI performed 2 months after treatment showed persistent pachymeningeal enhancement when her headaches were totally abated. Complete resolution of pachymeningeal abnormalities was secured between the second and the sixth month in the symptom free stage. Since striking reduction in the degree of dural enhancement can be seen in days or weeks with regard to the theories of pachymeningeal inflammation and dural venous dilatation,(15,16) the longer period of meningeal enhancement reflects the chronic nature of the underlying pathology. Thus, such an extended interval of dural enhancement as seen in our patient may suggest proliferative changes of the leptomeninges, which is a more plausible mechanism responsible for this delayed reversible phenomenon.

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From the Department of Neurology, Chang Gung Memorial Hospital, Kaoshiung.
Received: Apr. 30, 2002
Accepted: Aug. 29, 2002
Address for reprints: Dr. Jia-Shou Liu; Department of Neurology, Chang Gung Memorial Hospital. 123, Dabi Road, Niaosung Shiang, Kaohsiung, Taiwan 833, R.O.C.
Tel.: 886-7-7317123 ext. 3390;
Fax: 886-7-7317123 ext. 3399
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