Intracranial Hypotension

- The Low Pressure Headache

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, this unusual headache disorder can arise without a provoking medical procedure.



Spontaneous Intracranial Hypotension probably affects about 50 people per million every year.

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 (called cervical or thoracic root diverticula).

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 MRI Brain with 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 lowering of pressure is due to a loss of supporting pressure from the spine (technically a loss of compliance!). This is usually due to leakage of Cerebrospinal Fluid or CSF from a spontaneous tear in the lining of the spinal canal.

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

Diagnosis and Treatment of Intracranial Hypotension

One difficulty is that this condition can go unrecognised for weeks or months unless the improvement in symptoms on lying down is identified as part of the history taking process.

Some people with this condition will present with an exercise induced headache or even a thunderclap headache. These more sudden onset headaches are then followed by more typical postural symptoms.

An MRI Brain with gadolinium contrast is needed to see the classic change of "dural enhancement". An MRI myelogram study might show the point of leakage of fluid, but sometimes a CT myelogram is needed for this.

The treatment of choice is an epidural blood patch. Under sterile conditions about 10-20 mls of blood are drawn from the arm. They are then injected into the spine.

This injection of blood increases the supporting pressure within the spinal canal. This makes it less likely that the brain will sag down and stretch the pain-sensitive lining of the brain.

Some people require several epidural blood patch procedures over a period of weeks to get relief.

Cases that don't respond to blood patches with a known point of fluid leak could be referred for surgical exploration of the point of CSF leak.

You could read more about Back of Head Headaches

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