Diffuse meningeal enhancement on MRI with gadolinium contrast can confirm the diagnosis of intracranial hypotension when a patient presents with orthostatic headaches, said Todd J. Schwedt, M.D., a neurology fellow at the Mayo Clinic in Scottsdale, Ariz.
Patients who present with ongoing severe, diffuse, pressure headache that is worse when standing and relieved upon lying down may have intracranial hypotension due to a cerebrospinal fluid (CSF) leak. They may also experience very intense pain whenever they sneeze or cough, or with Valsalva maneuvers. The headaches may also be accompanied by vomiting and diminished hearing. Caffeinated beverages provide some relief from the headaches.
The differential diagnosis for orthostatic headache includes spontaneous intracranial hypotension (as in these cases), postdural puncture (resulting from a lumbar puncture or spinal anesthesia), and CSF fistula. Additional symptoms of spontaneous intracranial hypotension due to CSF leak can include diplopia, dizziness, visual blurring, interscapular pain, and radicular, upper extremity symptoms.
On MRI of the brain with gadolinium contrast, the classic sign of intracranial hypotension due to a CSF leak is contiguous, pachymeningeal enhancement, Dr. Schwedt said. Spontaneous CSF leaks also can cause generalized sagging of the brain with downward displacement of the cerebellar tonsils that is clearly visible on MRI with gadolinium.
MRI of the spine with and without contrast may not be as helpful. Despite the presence of a CSF leak, spinal MRIs may appear normal, with no visible collection of CSF. On occasion, spinal MRI may show pooling of extraarachnoid CSF, but this rarely identifies the exact location of the leak.
Autologous epidural blood patch is used to treat the CSF leak, even when MRI has not located the exact site of the leak. A history of minor trauma, orthostatic headaches, hearing changes, and MRI findings are considered reason enough to perform the blood patch.
For an epidural blood patch, 10–20 mL of autologous blood is injected into the epidural space. “Injection into the lumbar region can be adequate since the blood may travel to the site of the dural leak and injection will result in elevated CSF pressure,” Dr. Schwedt said.
Although the exact mechanism by which an epidural blood patch provides relief of symptoms is controversial, pain relief may be due to the formation of a gelatinous tamponade that stops the CSF leak and provides an immediate elevation of CSF pressure. Alternatively, the patch may increase CSF pressure by compression of the thecal sac, effectively reducing the volume of the intrathecal space. Relief usually occurs fairly quickly–within 30 minutes in many cases. The technique is typically performed by anesthesiologists.
Performing a lumbar puncture to see if a patient with such symptoms has a low opening pressure is an option. The CSF pressure may or may not be low, and the CSF may contain increased levels of protein and erythrocytes. However, given the diffuse meningeal enhancement seen on MRI and the clinical presentation, a clinical diagnosis can be made and a lumbar puncture avoided, as it has the potential to worsen the patient's symptoms.
Axial MRI with gadolinium contrast shows diffuse contiguous pachymeningeal enhancement (left). Without gadolinium (center), MRI looks normal. There was no evidence of cerebellar descent in this sagittal MRI with gadolinium. Photos courtesy Dr. Todd J. Schwedt
