Spontaneous Intracranial Hypotension

A spontaneous cerebrospinal fluid leak (SCSFL) is a medical condition in which the cerebrospinal fluid (CSF) surrounding the human brain and spinal cord leaks out of the surrounding protective dural sac for no apparent reason. The dura, a tough, inflexible tissue, is the outermost of the three layers of the meninges, the system of membranes surrounding the brain and spinal cord. A spontaneous cerebrospinal fluid leak (SCSFL) is a medical condition in which the cerebrospinal fluid (CSF) surrounding the human brain and spinal cord leaks out of the surrounding protective dural sac for no apparent reason. The dura, a tough, inflexible tissue, is the outermost of the three layers of the meninges, the system of membranes surrounding the brain and spinal cord. A spontaneous CSF leak, as opposed to traumatically caused CSF leaks, arises idiopathically. It is one of several types of cerebrospinal fluid leaks and occurs due to the presence of one or more holes in the dura. A loss of CSF greater than its rate of production leads to a decreased volume inside the skull known as intracranial hypotension. Any CSF leak is most often characterized by orthostatic headaches, which worsen in a vertical position and improve when lying down. Other symptoms can include neck pain or stiffness, nausea, vomiting, dizziness, fatigue, and a metallic taste in the mouth. A CT scan can identify the site of a cerebrospinal fluid leakage. Once identified, the leak can often be repaired by an epidural blood patch, an injection of the patient's own blood at the site of the leak, a fibrin glue injection, or surgery. When the cause cannot be identified, the set of symptoms is referred to as spontaneous cerebrospinal fluid leak syndrome (SCSFLS). SCSFLS afflicts 5 out of every 100,000 people. On average, the condition develops at age 42, and women are twice as likely as men to develop the condition. Some people with SCSFLS chronically leak cerebrospinal fluid despite repeated patching attempts, leading to long-term disability due to pain. SCSFLS was first described by German neurologist Georg Schaltenbrand in 1938 and by American physician Henry Woltman of the Mayo Clinic in the 1950s. SCSFLS is classified into two main types: cranial leaks and spinal leaks. The vast majority of leaks are spinal. Cranial leaks occur in the head. In some of these cases, CSF can be seen dripping out of the nose, or ear. Spinal leaks occur when one or more holes form in the dura along the spinal cord. Both cranial and spinal spontaneous CSF leaks cause neurological symptoms as well as spontaneous intracranial hypotension (SIH), diminished volume, and pressure of the cranium. While this symptom can be referred to as intracranial hypotension, the intracranial pressure may be normal, with the underlying issue instead being low CSF volume. For this reason, SCSFLS is referred to as CSF hypovolemia as opposed to CSF hypotension. Most people who develop SCSFLS feel the sudden onset of a severe and acute headache. This headache is usually made worse by standing and typically becomes prominent throughout the day, with the pain becoming less severe when lying down. Orthostatic headaches can become chronic and disabling to the point of incapacitation. Some patients with SCSFLS will develop headaches that begin in the afternoon. This is known as second-half-of-the-day headache. This may be an initial presentation of a spontaneous CSF leak or appear after treatment such as an epidural patch, and likely indicates a slow CSF leak. Apart from headache, about 50% of patients experience neck pain or stiffness, nausea, and vomiting. Other symptoms include dizziness and vertigo, facial numbness or weakness, unusually blurry or double vision, neuralgia, fatigue, or a metallic taste in the mouth. Leaking CSF can sometimes be felt or observed as a discharge from the nose or ear. Lack of CSF pressure and volume can allow the brain to sag and descend through the foramen magnum (large opening) of the occipital bone, at the base of the skull. The lower portion of the brain is believed to stretch or impact one or more cranial nerve complexes, thereby causing a variety of sensory symptoms. Nerves that can be affected and their related symptoms are detailed in the table at right. Several complications can occur as a result of SCSFLS including decreased cranial pressure, brain herniation, infection, blood pressure problems, transient paralysis, and coma. The primary and most serious complication of SCSFLS is spontaneous intracranial hypotension, where pressure in the brain is severely decreased. This complication leads to the hallmark symptom of severe orthostatic headaches. People with cranial CSF leaks, the rarer form, have a 10% risk of developing meningitis per year. If cranial leaks last more than seven days, the chances of developing meningitis are significantly higher. Spinal CSF leaks cannot result in meningitis due to the sterile conditions of the leak site. When a CSF leak occurs at the temporal bone surgery becomes necessary in order to prevent infection and repair the leak. Orthostatic hypotension is another complication that occurs due to autonomic dysfunction when blood pressure drops significantly. The autonomic dysfunction is caused by compression of the brainstem, which controls breathing and circulation.