Clinical History
A 40-year-old female patient presented with a history of severe headache which lasted for 1 month and that was subsiding in a recumbent position and was not relieved by the intake of common
analgesics. At lumbar puncture, the CSF opening pressure was found to be low (60 mm H2O) while the CSF was clear and the cytochemical analysis revealed no abnormalities. Four months later,
the patient’s symptoms subsided without any treatment except bedrest.
Imaging Findings
A 40-year-old male patient was admitted to the hospital complaining of a history of one-month severe headache, nausea and neck stiffness. The symptoms were subsiding in recumbent position and did not
respond to the common analgesics. The neurological and general physical examination showed no abnormalities. An MRI of the brain demonstrated a diffuse smooth thickening of the duramater, sparing the
basal cisterns and extending down to the ventral aspect of the cervical spine down to the C3 vertebra. The duramater showed a high signal intensity in T2 weighted (Fig. 1a) and FLAIR (Fig. 1b) (fluid
attenuation inversion recovery) images and an intermediate signal in T1 weighted images. After iv contrast administration (Gd-DTPA), the duramater was intensely and diffusely enhanced (Fig. 1c).
There were signs indicative of caudal displacement of the brain including slit like ventricles, decrease of the anteroposterior diameter of the prepontine cistern (PS) and anterior subarachnoid space
(ASS) (PS=3.4 mm, ASS=1.7 mm) and low position of the iter (2.2 mm below the incisura line, normal values: 0.20.8 mm). The cerebellar tonsils were in a normal position. An
increase of the pituitary gland height (PGH=7 mm, normal values for age: 5.351.2) was observed (Fig. 2). An MR myelography was performed which revealed no signs of potential CSF
leakage. Gram and Indian stains, stains for acid fast bacteria and cryptococcal antigen in the CSF examination were found to be negative. Tuberculin skin test and serological tests for EBV,
Toxoplasma, CMV, Borrelia and RPR were also found to be negative. The results of autoimmunity screening tests were found to be normal. The patient’s symptoms completely subsided four months
later, without any treatment except bedrest. A new MRI of the brain was performed which showed a normal looking duramater with no contrast enhancement (Fig. 3a). The size of the prepontine cistern
and anterior subarachnoid space increased (PS=6.7 mm, ASS=3.6 mm), the iter was in a normal position (0.8 mm below the incisura line) and the PGH was within normal values for age and sex (PGH=4.8mm)
(Fig. 3b). The diagnosis of spontaneous intracranial hypotension (SIH) was made according to the clinical, laboratory and imaging findings.
Discussion
Intracranial hypotension (IH) is a clinical condition presenting with a headache aggravated by the upright position and not responding to the administration of common analgesics [1]. Other symptoms
may coexist including nausea, neck stiffness, vertigo and tinnitus. The causes that lead to IH is a CSF leak due to a dural trauma (e.g. diagnostic lumbar puncture, craniospinal surgery, skull base
trauma) or due to the presence of Tarlov’s cyst and/or arachnoid diverticula. When no cause of CSF leak is found, the condition is considered as spontaneous intracranial hypotension (SIH) [2].
The syndrome is characterized by low opening pressure at lumbar puncture (<60 mm H2O), while the cytochemical analysis is within normal values or shows increased protein and white cell
count [2]. The most common and pronounced MR imaging finding of SIH is the diffuse smooth thickening of the dura associated with intense contrast enhancement [2]. Both are considered to be the result
of venous dilation that follows the decrease of the CSF volume produced by the leakage. According to the Monro–Kellie doctrine [3], the intracranial volume of CSF is inversely related to the
brain blood volume. Thus, in SIH a decrease of the CSF volume leads to an increase of the dural blood volume and venous engorgement. Furthermore, when venous engorgement becomes chronic,
fibrocollagenous proliferation contributes to the dural thickening as well. These findings are limited to the upper cervical spine since the vasculature of the dura is less prominent in the spinal
canal. Another reason for this limited involvement is the fact that the Monro–Kellie doctrine does not strictly imply to a more expansile system such as the spinal canal. Thickening and
enhancement of the dura are not specific findings and other serious conditions, including infectious and malignant meningitis, have to be excluded. The differential diagnosis is based on the diffuse,
continuous and smooth involvement of the dura, the sparing of the basal cisterns and the CSF findings [4]. Another morphological MR finding that characterizes SIH is the downward displacement of the
brain that is responsible for the traction that is produced on the cranial and the upper cervical nerves and the postural headache. The MR signs indicating descent of the brain are the decrease in
the size of the ventricles and the basal cisterns, decrease of the anteroposterior diameter of the prepontine cistern and the anterior subarachnoid space and the downward displacement of the iter
[1]. More than one of these signs is mandatory for the diagnosis since many of them might be subtle when examining the patient in the supine position. It is of interest to mention that the descent of
the cerebellar tonsils is a late manifestation of IH. The increase in the PGH observed in this case has also been previously described [5]. A possible mechanism of this increase is the venous
engorgement at the level of the duramater covering the sella turcica. The morphological MR imaging findings of SIH, although not specific, are characteristic and in association with the clinical and
other laboratory findings provide valuable information for the diagnosis of this syndrome.
Differential Diagnosis List
Spontaneous intracranial hypotension.
Final Diagnosis
Spontaneous intracranial hypotension.
