Cerebrospinal fluid (CSF) is a transparent, colourless fluid that is essential to the health and operation of the central nervous system. It acts as a cushion for the brain and spinal cord, supplies nutrients and clears away waste products.
Although it is vital, issues involving CSF can remain undetected until they begin to cause problems.
As a neurologist and headache specialist who treats people with CSF pressure disorders, I have encountered conditions that can appear in numerous ways. Here is what can occur when cerebrospinal fluid no longer functions properly.
What is cerebrospinal fluid?
CSF contains water, proteins, sugar, ions and neurotransmitters. It is produced mainly by the choroid plexus, a network of cells found within the brain’s ventricles, or cavities.
The choroid plexus generates roughly 500 millilitres of CSF each day. Yet, because the fluid is continually absorbed and replaced in the brain, only around 150 millilitres are present in the central nervous system at any one time.
The fluid moves through the brain’s ventricles, the spinal cord’s central canal and the subarachnoid space around the brain and spinal cord.
CSF performs several essential roles. By absorbing impacts, it shields the brain and spinal cord from injury. Keeping the brain suspended in fluid reduces its effective weight, helping to stop it from being compressed by its own mass.
It also supports a consistent chemical environment within the central nervous system by helping to remove metabolic waste and distribute nutrients and hormones.
Disruption to the production, movement or absorption of cerebrospinal fluid can cause serious health problems. CSF leaks and idiopathic intracranial hypertension are two important examples.
CSF leak
A CSF leak develops when the fluid passes through a tear or opening in the dura mater - the robust outer layer of the meninges surrounding the brain and spinal cord.
Head trauma can damage the dura, while procedures involving the sinuses, brain or spine can puncture it. These include lumbar punctures, epidurals, spinal anaesthesia and myelograms. Spontaneous CSF leaks may also arise without an identifiable cause.
CSF leaks were once considered comparatively uncommon, with an estimated yearly incidence of 5 per 100,000 people. Greater awareness and improved imaging mean that healthcare professionals are now identifying increasing numbers of leaks. They occur more often in middle-aged adults and are more common among women than men.
Risk factors include connective-tissue conditions, such as Ehlers-Danlos syndrome, and postural orthostatic tachycardia syndrome.
CSF leaks are unfortunately often mistaken for other illnesses, including migraine, sinus infections or allergies. Their wide-ranging symptoms can make them difficult for healthcare professionals to diagnose.
Most people with a CSF leak develop a positional headache: it eases when they lie down and becomes worse when they stand. The pain is generally located at the back of the head, and can extend to the neck and the area between the shoulder blades.
Alongside headache, patients can experience tinnitus, visual disturbances, memory difficulties, brain fog, dizziness and nausea.
Scans can assist diagnosis. These may include an MRI of the brain or entire spine, or a myelogram of the space around the spinal cord. Imaging signs of a CSF leak can include the brain sagging towards the base of the skull and a collection of fluid outside the dura.
However, scans are normal in an estimated 19% of people with a CSF leak. Therefore, the absence of visible evidence on imaging does not completely exclude a leak.
Conservative treatment involves rest, remaining flat and increasing fluid intake, allowing time for the spinal puncture to heal. Raising caffeine intake to the equivalent of three to four cups of coffee daily may also help, as caffeine stimulates the choroid plexus and increases CSF production.
Caffeine can also lessen pain through its interaction with adenosine receptors, which have a key role in the body’s mechanisms for perceiving pain.
When conservative treatment does not succeed, an epidural blood patch may be required. For this procedure, blood is taken from the arm and injected into the spine. The blood may create a seal over the opening and support healing.
Headaches may improve quickly. But if the blood patch fails or its effects do not last, further tests may be required to pinpoint the leak more accurately. Surgery is occasionally advised in rare cases. Most people with a CSF leak respond to one of these treatments.
Idiopathic intracranial hypertension
Idiopathic intracranial hypertension is a condition in which excessive CSF raises pressure inside the skull and compresses the brain. The word "idiopathic" means that the source of the increased pressure is unknown.
Most people with idiopathic intracranial hypertension have obesity or have recently gained weight. Additional risk factors include certain medicines, such as tetracycline, excessive vitamin A, tretinoin, steroids and growth hormone.
Middle-aged women with obesity are 20 times more likely to receive a diagnosis of idiopathic intracranial hypertension than other patient groups. As obesity becomes more widespread, the occurrence of this condition rises too.
People with idiopathic intracranial hypertension commonly have headaches, changes to vision, tinnitus or eye pain. Papilloedema - swelling of the optic disc - is the characteristic finding when the back of the eye is examined with a fundoscopy. Clinicians may also identify paralysis affecting the patient’s eye muscles.
Brain imaging is essential when idiopathic intracranial hypertension is suspected, as it rules out other causes of raised CSF pressure, including brain tumours and blood clots in the brain. A lumbar puncture, or spinal tap, is also central to diagnosis because it measures CSF pressure and composition.
Raised intracranial pressure can harm the optic nerve and cause permanent loss of vision. Treatment therefore focuses first on lowering pressure and protecting the optic nerve. Options include weight loss, dietary adjustments and medicines that reduce CSF production. Surgical procedures may also lower intracranial pressure.
Future directions and unknowns
Cerebrospinal fluid is indispensable to brain health, but several questions remain despite progress in understanding CSF-related diseases.
The precise processes causing conditions such as CSF leaks and idiopathic intracranial hypertension have not been fully established, although many theories exist.
Further research is essential to improve diagnostic precision and identify effective treatments for CSF disorders.
Danielle Wilhour, Assistant Professor of Neurology, University of Colorado Anschutz Medical Campus
This article is republished from The Conversation under a Creative Commons licence. Read the original article.
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