Intracranial Hypotension

- The Low Pressure Headache

Spontaneous Intracranial Hypotension is a severe headache disorder caused by leakage of cerebrospinal fluid into the spinal canal.

It is being diagnosed more often as understanding and acceptance of its symptoms and causes are better understood.

Since the first lumbar punctures were performed in the 1800's it has been known that low pressure headaches could occur as a result of persistent cerebrospinal fluid leakage at the site of a spinal needle insertion.

However, the fact that this condition can arise without a provoking medical procedure is what makes this disorder fascinating.

It now appears that cerebrospinal fluid leaks can occur spontaneously, usually from areas of weakness in the meningeal lining of nerve roots in the spinal canal (cervical or thoracic).

To make a diagnosis, it is important the condition is specifically considered by the clinician and that the radiologist is aware that you suspect this condition.

The changes of low pressure can be subtle and require gadolinium injection to see pachymeningeal enhancement. A plain or contrast enhanced CT Brain will not show changes.

Diagnosis relies on a history of a postural headache, also called orthostatic headache.

A postural headache is one that is better on lying flat and is worse on standing.

There is a phenomenon called "second half of day" headache. These people are OK on rising in the morning, but as the day proceeds a worsening headache occurs, which is once more relieved by lying flat.

The criteria for diagnosis of spontaneous low pressure headaches have recently been revised by Schievink, Maya and Moser (2008).

The Headache of Intracranial Hypotension

This loss of fluid, causes the supporting fluid of the brain - called Cerebrospinal Fluid or CSF - to leak out.

The brain starts to sag within the skull. The lining of the brain (meninges) are very sensitive. It is this stretching of the brain lining (meninges) which causes the pain.

On lying flat, there is a lot less need for the brain to be supported, so symptoms ease, as the meninges are not being stretched so much.

Classically the pain is located in both temples, but in reality it can occur anywhere in the head. It can have an aching or pressure quality to it, so can easily be confused with tension-type headache if the history of postural headache is not elicited.

Other Symptoms caused by Cerebrospinal Fluid Leak

1. Most Common Symptoms 90-100%
• Headache
• Neck Pain
2. Fairly Common 25-50%
• Nausea, especially provoked on standing
• Hearing problems (tinnitus, deafness)
3. Less Common Symptoms c5%
• Double Vision
• Tremor
• Coma or Confusion
• Galactorrhoea
• Tingling of hands and feet