Orthostatic or Post LP Headache
Orthostatic Headache – Symptoms – Headache Type – Causes – Treatment
Orthostatic or Post LP Headache
Orthostatic headache is a dull and pulsating headache which sometimes may be pretty disabling. It is brought up by a vertical body position.
The headache is alleviated significantly by a horizontal body position and upon exertion or straining.
Orthostatic headache is caused by a low intracranial pressure. Intracranial means “inside the skull” – the compartment where the brain is situated.
The most common reason for a low intracranial pressure is a leakage of the cerebrospinal fluid.
Symptoms of Orthostatic Headache
There is a rapid or a gradual onset of the headache upon arising with a “thunderclap headache” features in 15%. The rest will have milder pain which tends to deteriorate as the day goes on. Whether the pain is bad or mild, there is a predictable relief of pain in horizontal position and during straining.
The pain quality is a dull poorly localized headache with a tendency of becoming pulsatile. Orthostatic headache typically involves both sides of the head and tend to be frontal, occipital or holocranial.
Associated symptoms of a stiff neck, nausea, vomiting, blurred vision, pulsatile noise in the ears, and shooting pain to the upper limbs are not uncommon.
Orthostatic headache typically resolves within a few days but in some people it may become chronic.
Mechanism of Orthostatic Headache
The brain and the spinal cord are very delicate structures. They are suspended in the fluid which is called cerebrospinal fluid or CSF. Imagine yourself floating in a bathtub. Pounding the tub with a large hammer will not affect you, because you are protected by the surrounding water. The brain is protected from a mechanical damage by this fluid.
Since the fluid is contained within a limited volume it has a certain level of pressure. CSF production and absorption is tightly controlled in order for the pressure to be maintained at a certain physiological level. When the body position is changed to vertical, the cerebrospinal fluid is obviously rushing down. If the pressure is normal, no significant displacement of the brain within the skull occurs while being upright.
When the CSF pressure is low, the brain along with the meninges is displaced downwards due to gravity force. This displacement stretches meninges (pain sensitive membranes, covering the brain).
The meninges are rich in the blood supply. Blood vessels are pain sensitive and they are apparently pulsating. This is why stretched meninges produce a severe pain complicated by a pounding or “pulsating” component.
Causes of a Low CSF Pressure
The cause of a low CSF pressure is typically a CFS leak due to loss of the meninges integrity in some place.
The most common cause of a CSF leak is a defect in the meninges due to a spinal tap or an epidural injection. Orthostatic headache typically begins within 48 hours after the procedure, or the headache onset may be delayed for as long as 2 weeks.
Head injuries complicated by a fractured skull base may cause CSF leakage through the nose. A dripping CSF from the nose while bending over is a classical description of this phenomenon. In this case the leakage and the cause of such are clear.
Occasionally, this condition may develop spontaneously without apparent prior injury or an invasive procedure.
Other potential reasons for the CSF leak are neurosurgical procedures, trauma (even without apparent bone fractures), anatomical abnormalities of the meninges in the spine, tumor invasion, and genetic disorders, such as Marfan and Ehler-Danlos syndromes.
Some cases of orthostatic headaches are not associated with any CSF leakage. Low intracranial pressure may be caused by dehydration, uremia, or some medications (Diamox).
Overdrainage in patients with CSF shunts is another possibility.
Diagnosis of Orthostatic Headache
Brain MRI reveals a thickening and contrast enhancement of the meninges. There could be other changes secondary to the low intracranial pressure: downward displacement of the cerebellar tonsils, subdural effusions, enlarged pituitary and spinal epidural veins.
All those abnormalities allow to suspect a decreased intracranial pressure but they give no clue about the source of the CSF leak.
Recent history of a spinal tap is helpful.
Recent head injury and a watery discharge from the nose also points to the specific location. The nose discharge may be tested for beta-2 transferin, which is very specific for the CSF. The test is very sensitive and accurate.
Finding a CSF leak site without any symptomatic clues is a challenging task.
Most common diagnostic modalities are myelogram/CT myelogram and an indium radioisotope cisternogram. An interpretation of those tests regarding CSF leakage is complicated and they might miss a small leak or fail to pinpoint the exact location.
Treatment of Orthostatic Headache
Post lumbar puncture headache is normally managed by a bed rest. Caffeine may offer a temporary headache relief.
Cerebrospinal fluid leakage at the spine level is managed by an epidural blood patch. In this procedure the patient’s own blood is injected in the epidural space.
Sometimes a direct surgical repair is required if an epidural blood patch is ineffective or is not practical due to the leakage location.
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