This 53-year-old woman presents with non-intractable headache with unspecified chronicity pattern and unspecified headache type. Patient states no known injury, with pain at the base of head and across the forehead when bending or rotating her head for three months. She is pre-diabetic with no cancer or surgery. What diagnosis is suggested by this history and the findings in the images below? Be sure to start with the sagittal T2 FLAIR (image 1), as it tells much of the story.
The following findings are indicated by arrows in image 1 and are crucial to the diagnosis.
- Engorged venous sinus and deep cerebral veins (orange arrow)
- Splenium of corpus callosum depression or flattening internal cerebral vein/vein of Galen junction (yellow arrow)
- Closed midbrain angle (green arrow)
- Effaced prepontine cistern (purple arrow)
- Cerebellar tonsil descent (blue arrow)
You should also take note of the diffuse pachymeningeal (dural) thickened smooth enhancement (images 4 and 5, arrows). This constellation of findings is compatible with intracranial hypotension (IH) and consistent with the patient’s clinical syndrome. A common cause of IH is a spontaneous cerebrospinal fluid (CSF) leak. A weak dura and/or arachnoid diverticulae is also common, and you should look for aberrant extracellular matrix with abnormalities of fibrillin-containing microfibrils. Most, but not all, cases caused by reduced CSF pressure are precipitated by:
- Surgery (CSF overshunting) or trauma (including trivial fall)
- Vigorous exercise or violent coughing
- Diagnostic lumbar puncture or post-operative spine leak
- Spontaneous dural tear, ruptured arachnoid diverticulum
- Severe dehydration
- Disc herniation or osteophyte (rare)
As for the pathophysiology, follow the Monro-Kellie doctrine. The CSF and intracranial blood volume vary inversely. In the face of low CSF pressure, the dural venous plexuses dilate. Other associated abnormalities include dilated cervical epidural venous plexus, spinal hygromas and retrospinal fluid collections.
It is typical to see a low opening pressure of less than 6 cm water. The CSF also frequently shows pleocytosis and increased protein. The OP (opening pressure) is occasionally normal, but this is indicative of CSF hypovolemia rather than hypotension.
Stigmata of systemic connective tissue disorder is found in up to 2/3 of patients with spontaneous unexplained CSF hypotension. Look for Marfan syndrome and Ehlers-Danlos syndrome type 2 in patients with unexplained intracranial CSF hypotension. Clinical findings of connective tissue disease can include minor skeletal fractures, small joint hypermobility, etc. These findings may be subtle.
PROSCAN PEARL: Finally, in any patient with postural headache, be suspicious of intracranial hypotension.
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