Low-pressure headache

Headaches caused by drainage of cerebrospinal fluidThis clear, water-like fluid forms, for the most part, within the brain, more specifically inside the ventricles of the brain. Blood flows through structures inside the ventricles, called the choroid plexuses, and clear fluid is produced as a result, passing into the ventricle. This process is akin to blood flowing through the kidneys and urine being produced as a result. An important difference is that, unlike urine, the cerebrospinal fluid is not passed out of the body periodically. Instead, the fluid is re-absorbed back into the blood stream, mostly via the arachnoid granulations, into the cerebral venous sinuses. In the course of a 24-hour period, most healthy adults will produce about 500mls (or a pint) of cerebrospinal fluid, although at... from the head. This drainage may follow a lumbar punctureA long needle is passed into the lower part of the spine, in order to remove some cerebrospinal fluid. This may be to reduce pressure within the head or to obtain a sample of the fluid for laboratory analysis. or be via an implanted cerebrospinal shuntA shunt shifts one object, or volume of fluid (or gas or electrical current), from one place to another. In the context of neurosurgical practice we are considering cerebrospinal fluid, which is diverted from the ventricles of the brain, or the spinal theca, into another part of the body, most often the peritoneal cavity. system. See also spontaneous intracranial hypotensionA rare condition in which cerebrospinal fluid leaks, spontaneously, from the theca which lines the spinal canal. The fluid that drains out of the spine and the head causes the brain to lose buoyancy. The brain slumps downwards and pulls on the arteries that supply it with blood. It also presses on the membranes that line the skull. These structures contain nerve fibres which then send pain signals to the brain itself and which are perceived as headaches. The headaches of spontaneous intracranial hypertension characteristically develop or are made worse when the affected individual is upright for a period and are relieved by lying down. In this respect they are similar to the low-pressure headaches that develop after a lumbar....