What is intracranial hypotension?
Q: My friend's wife was in the hospital for suspected meningial hypotension. It is a neurological problem, can you brief me about this? Is it curable? What is the treatment required? Does it involve bedrest?
A:The brain and the spinal cord are covered by a membrane called meninges which is made up of several layers (duramater, arachnoid and piamater). Cerebrospinal fluid (CSF) is a clear fluid produced by the brain that occupies the subarachnoid space in the brain (i.e.the space between the arachnoid and pia layers of the meninges). The CSF is formed by the choroid plexus of the brain, circulates through the brain and spinal cord and is finally absorbed by the venous system. This fluid acts as a cushion for the brain and is responsible for maintaining pressure called the intracranial pressure. Escape of this fluid leads to a fall in pressure, a condition referred to as intracranial hypotension. Imaging techniques of the brain reveal diffuse meningeal enhancement. A very important feature of this condition is the large discrepancy between the clinical appearance of the patient and the MRI findings. The changes seen represent reactive secondary phenomena, likely related to hydrostatic changes in the CSF, and not a condition which primarily affects the meninges. This condition is characterized by an orthostatic headache, that is, one that occurs or worsens with upright posture, although some patients may have chronic headache or even no headache. The nature and location of the headache vary greatly from patient to patient; but consistently the pain is exacerbated by laughing, coughing, etc. and is resistant to treatment with analgesics. In addition to headache, patients may experience nausea, vomiting, lack of appetite, neck pain, dizziness, horizontal diplopia, changes in hearing, galactorrhea, facial numbness or weakness, or radicular symptoms involving the upper limb, all of which are orthostatic in nature. It is caused by a leak of CSF which may occur following a lumbar puncture or other invasive procedures like myelography, spinal anesthesia, spinal surgery, trauma, or placement of a ventriculoperitoneal shunt.Medical causes include dehydration, diabetic coma, hyperpnea (hyperventilation), uremia, and severe systemic illness. Less common are spontaneous spinal CSF leaks when an anatomical cause often cannot be found. It is considered to be a benign condition and most cases resolve with conservative management - bed rest and high fluid intake. It is thought that lying down reduces CSF pressure at the site of leakage and therefore allows healing of the underlying meningeal defects. Symptoms, however, can take several months to resolve. The intake of caffeine is recognized in helping to ameliorate symptoms because it helps to maintain intracranial pressure. If conservative measures fail, other treatments aimed at increasing CSF volume are resorted to. This may be done by intravenous or oral hydration, increased salt intake, carbon dioxide inhalation, and steroid therapy sealing the leak using epidural blood patches. Rarely open surgical procedure may be required.