About Intracranial Hypotension

General Information

• 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 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.
• 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.

Symptoms

• The classic 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 options 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.