Intracranial Hypotension
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About Intracranial Hypotension
- Intracranial hypotension is a condition in which there is negative pressure within the brain cavity.
- There are several possible causes:
- Cerebrospinal fluid (CSF) leak from the spinal canal:
- A leak following a lumbar puncture (spinal tap)
- A defect in the dura (the covering on the spinal tube)
- Spontaneous, sometimes following exertion such as swinging a golf club
- A congenital weakness
- Following spinal surgery
- Following spinal trauma
- Following a shunt procedure for hydrocephalus.
- Lumboperitoneal shunt
- Ventriculoperitoneal shunt with a low pressure valve
- Cerebrospinal fluid (CSF) leak from the spinal canal:
- In some cases, spinal CSF leaks can lead to a descent of the cerebellar tonsils into the spinal canal, similar to a Chiari malformation.
- Large spinal dural defects can lead to herniation of the spinal cord into the defect.
Intracranial Hypotension Symptoms
- The classic intracranial hypotension symptom is severe headache when upright, which is relieved when lying flat.
- Other symptoms can include nausea, vomiting, double vision and difficulty with concentration.
Diagnosis
- Diagnosis is usually suspected based on the postural dependency of the headache, although in many cases the diagnosis of intracranial hypotension is not considered for some time.
- A contrast-enhanced brain magnetic response imaging (MRI) scan typically shows thickened and brightly enhancing meninges (pachymeningeal enhancement). Other findings include descent of the thalamus and cerebellar tonsils.
- Continuous intracranial pressure monitoring is definitive for documenting abnormally negative intracranial pressures.
- The identification of the site of CSF leak in the spinal canal can be very challenging. In some cases, the site cannot be identified. Methods include:
- Dynamic myelography with fluoroscopy and computed tomography (CT)
- Radioisotope cisternography
- Spinal MRI
Treatment
- If the site of the spinal CSF leak can be identified, then treatment options for intracranial hypotension include:
- Epidural blood patch, performed by an anesthesiologist pain management specialist
- Surgical repair of the defect
- Over-draining CSF shunts are managed by replacing the valve with one that drains less.
- Lumboperitoneal shunts may have to be removed or ligated
Outcome
- If the cause of the intracranial hypotension can be identified, the outcome following treatment is typically excellent.