cerebrospinal fluid leak cerebrospinal fluid leak a cerebrospinal fluid leak (csf leak or csfl) is a medical condition where the cerebrospinal fluid (csf) surrounding the brain or spinal cord leaks out of one or more holes or tears in the dura mater. a cerebrospinal fluid leak can be either cranial or spinal, and these are two different disorders. a spinal csf leak can be caused by one or more meningeal diverticula or csf-venous fistulas not associated with an epidural leak. cerebrospinal fluid leakother namescsf leakthe spinal meninges of the central nervous system impacted by csf leakspecialtyneurology a csf leak is either caused by trauma including that arising from medical interventions or spontaneously sometimes in those with predisposing conditions (known as a spontaneous cerebrospinal fluid leak or scsf leak). traumatic causes include a lumbar puncture noted by a post-dural-puncture headache, or a fall or other accident. spontaneous csf leaks are associated with heritable connective tissue disorders including marfan syndrome and ehlers–danlos syndromes. 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 when standing, 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 myelography 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. the set of symptoms associated with a scsf leak is referred to as a spontaneous cerebrospinal fluid leak syndrome (scsfls). a scsf leak is a rare condition, affecting at least one in 20,000 people and many more who go undiagnosed every year. on average, the condition develops at age 42, and women are twice as likely to be affected. some people with a scsf leak have a chronic leak of cerebrospinal fluid despite repeated patching attempts, leading to long-term disability due to pain and being unable to be upright, and surgery is often needed. scsfls was first described by german neurologist georg schaltenbrand in 1938 and by american neurologist henry woltman of the mayo clinic in the 1950s. classification spontaneous cerebrospinal fluid leaks are classified into two main types: cranial leaks, and spinal leaks. the vast majority of leaks are spinal. cranial leaks occur in the head, and in some of these cases, csf can leak from the nose, or from the 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, 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, a scsfl is referred to as csf hypovolemia as opposed to csf hypotension. spontaneous intracranial hypotension, a subtype of csf leak, refers to lower than normal than csf volume due to an initially unknown or insidious cause. this differentiates it from csf leaks of known causes such as cranial or spinal trauma, surgery or lumbar puncture or spinal anesthesia (most common cause of csf leak). the international classification of headache disorders (ichd) third edition diagnostic criteria for spontaneous intracranial hypotension includes any headache attributed to low csf pressure (low csf opening pressure) or csf leakage (evidence of csf leakage on imaging). further, the headache must have a temporal relation to the low csf pressure or leakage and the headache cannot be better explained by another ichd diagnosis. the final criteria is that in the rare cases of spontaneous intracranial hypotension with no headache present, the neurologic symptoms that are present must be attributable to low csf or explained by the diagnosis of spontaneous intracranial hypotension. signs and symptoms symptoms resulting from nerve impact nervefunctionsymptoms optic (2)optic nerve crossingblurred and ordouble vision chorda tympani (branch of 7)tastetaste distortion facial (7)facial nervefacial weakness and numbness vestibulocochlear (8)hearing, balancehearing and balance problems glossopharyngeal (9)tastetaste distortion the most common symptom of a csf leak is a fast-onset, extremely painful orthostatic headache or thunderclap 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 a scsfl 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. while high csf pressure can make lying down unbearable, low csf pressure due to a leak can be relieved by lying flat on the back. about 50% of people with a csfl experience neck pain or stiffness, nausea, and vomiting. other symptoms of a csf leak include photophobia, dizziness and vertigo, gait disturbances, tinnitus, facial numbness or weakness, visual disturbances, brain fog or difficulties with concentration, neuralgia, fatigue, fluid dripping from the nose or ears, aural symptoms are also present in many cases of intracranial hypotension due to csf leak; including muffled hearing, pulsatile tinnitus, hearing loss. less common symptoms include double vision (due to cranial nerve 6 palsy) or tremor. movement disorders are uncommon in spontaneous csf leaks but occasionally can be one of the major components of the clinical presentation. some cases of chronic intracranial hypotension due to csf leak may present as personality changes, altered behaviors and impairment of executive functions, similar to behavioral-variant frontotemporal dementia as the frontal and temporal lobes are affected by downward sagging due to reduced intra-cranial pressures. an untreated csf leak can result in coma or death as late stage findings as the brainstem herniates through the skull base or foramen magnum . causes a spontaneous csf leak is termed so as it has previously been thought to be idiopathic, meaning the cause is unknown. the evidence of the last decade suggests however, that these leaks result from either a discogenic pathology, such as microspur, osteophyte or intra-dural disc herniation that pierces the dura like a knife, connective tissue disorder (which can often lead to discogenic pathology), or spinal drainage problems. a cerebrospinal fluid leak can be a rare complication of an anterior cervical discectomy and fusion (acdf). one study suggested a csf leak to follow from 0.5% of operations. another study suggests a csf leak to follow from 1% of operations. in most of these cases repair is successful. discogenic causes the most common cause of an intractable "scsf" leak is discogenic, either from an intra-dural disc herniation, osteophyte or microspur on the disc or vertebral body. "recent radiological and microsurgical investigations revealed that a calcified, degenerative bony microspur is often the culprit lesion in cases of intractable csf leaks. arising from the level of the intervertebrate disk space, these microspurs pierce the ventral dura and produce a slit-like defect a few millimeters in length. these microspurs and the associated csf leak have to be localized exactly, and then they are amenable to surgical treatment." connective tissue theory various scientists and physicians have suggested that scsfls may be the result of an underlying connective tissue disorder affecting the spinal dura. it may also run in families and be associated with aortic aneurysms and joint hypermobility. up to two thirds of those affected demonstrate some type of generalized connective tissue disorder. marfan syndrome, ehlers–danlos syndrome, and autosomal dominant polycystic kidney disease are the three most common connective tissue disorders associated with scsfls. roughly 20% of patients with a scsfl exhibit features of marfan syndrome, including tall stature, hollowed chest (pectus excavatum), joint hypermobility and arched palate. however, no other marfan syndrome presentations are shown. spinal drainage theory some studies have proposed that issues with the spinal venous drainage system may cause a csf leak. according to this theory, dural holes and intracranial hypotension are symptoms caused by low venous pressure in the epidural space. when inferior limb muscles pump blood towards the heart and pressure in the inferior vena cava vein becomes negative, the network of epidural veins is overdrained, causing csf to be aspirated into the epidural space. true leaks can form at weak points in the spinal meninges. therefore, the observed csf hypotension is a result of csf hypovolemia and reduced epidural venous pressure. other causes cranial csf leaks result from intracranial hypertension in a vast majority of cases. the increased pressure causes a rupture of the cranial dura mater, leading to csf leak and intracranial hypotension. patients with a nude nerve root, where the root sleeve is absent, are at increased risk for developing recurrent csf leaks. lumbar disc herniation has been reported to cause csf leaks in at least one case. degenerative spinal disc diseases cause a disc to pierce the dura mater, leading to a csf leak. csf leaks can result from a lumbar puncture procedure. complications arnold–chiari malformation is a condition where the cerebellar tonsils have descended, and should be considered in differential diagnosis of scsfls. 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. low csf volume can cause the cerebellar tonsil position to descend, which can be mistaken for chiari malformation; however when the csf leak is repaired the tonsil position often returns to normal (as seen in upright mri) in this "pseudo-chiari" condition. a further, albeit rare, complication of csf leak is transient quadriplegia due to a sudden and significant loss of csf. this loss results in hindbrain herniation and causes major compression of the upper cervical spinal cord. the quadriplegia dissipates once the patient lies supine. an extremely rare complication of scsfls is third nerve palsy, where the ability to move one's eyes becomes difficult and interrupted due to compression of the third cranial nerve. there are documented cases of reversible frontotemporal dementia and coma. coma due to a csf leak has been successfully treated by using blood patches and/or fibrin glue and placing the person in the trendelenburg position. empty sella syndrome, a bony structure that surround the pituitary gland, occurs in csf leak patients. pathophysiology cerebrospinal fluid is produced by the choroid plexus in the ventricles of the brain and contained by the dura and arachnoid layers of the meninges. the brain floats in csf, which also transports nutrients to the brain and spinal cord. as holes form in the spinal dura mater, csf leaks out into the surrounding space. the csf is then absorbed into the spinal epidural venous plexus or soft tissues around the spine. due to the sterile conditions of the soft tissues around the spine, there is no risk of meningitis. 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. diagnosis diagnosis of csf leakage can be done by various imaging techniques, chemical tests of bodily fluid discharged from a head orifice, or clinical examination. the use of