When cranial CSF leak is suspected because of discharge from the nose or ear that is potentially CSF, the fluid can be collected and tested with a beta-2 transferrin assay. This test can positively identify if the fluid is cerebrospinal fluid.

Magnetic resonance imaging is less effective than CT at directly imaging sites of CSF leak. MRI studies may show pachymeningeal enhancement (when the dura mater looks thick and inflamed), sagging of the brain, pituitary enlargement, subdural hygromas, engorgement of cerebral venous sinuses, and other abnormalities. For 20% of patients, MRIs present as completely normal. There is disagreement over whether MRI should be the study of choice. MRIs performed with the patient seated upright (vs. laying supine) are not better for diagnosing CSF leaks, but are more than twice as effective at diagnosing cerebellar tonsillar ectopia, also known as Chiari malformation. Cerebellar tonsillar ectopia shares many of the same symptoms as CSF leak, but originates either congenitally or from trauma, including whiplash strain to the dura.

An alternate method of locating the site of a CSF leak is to use heavily T2-weighted MR myelography. This has been effective in identifying the sites of a CSF leak without the need for a CT scan, lumbar puncture, and contrast and at locating fluid collections such as CSF pooling. Another highly successful method of locating a CSF leak is intrathecal contrast and MR Myelography.

Neuroimaging, usually with computed tomography (CT/CAT) or magnetic resonance imaging (MRI), is used to exclude any mass lesions. In IIH these scans typically appear to be normal, although small or slit-like ventricles, dilatation and buckling of the optic nerve sheaths and "empty sella sign" (flattening of the pituitary gland due to increased pressure) and enlargement of Meckel's caves may be seen.

An MR venogram is also performed in most cases to exclude the possibility of venous sinus stenosis/obstruction or cerebral venous sinus thrombosis. A contrast-enhanced MRV (ATECO) scan has a high detection rate for abnormal transverse sinus stenoses. These stenoses can be more adequately identified and assessed with catheter cerebral venography and manometry. Buckling of the bilateral optic nerves with increased perineural fluid is also often noted on MRI imaging.

Lumbar puncture is performed to measure the opening pressure, as well as to obtain cerebrospinal fluid (CSF) to exclude alternative diagnoses. If the opening pressure is increased, CSF may be removed for transient relief (see below). The CSF is examined for abnormal cells, infections, antibody levels, the glucose level, and protein levels. By definition, all of these are within their normal limits in IIH. Occasionally, the CSF pressure measurement may be normal despite very suggestive symptoms. This may be attributable to the fact that CSF pressure may fluctuate over the course of the normal day. If the suspicion of problems remains high, it may be necessary to perform more long-term monitoring of the ICP by a pressure catheter.

A cerebrospinal fluid leak (CSFL) is a medical condition where the cerebrospinal fluid(CSF) in the brain leaks out of the dura mater. This can be due to a spontaneous cerebrospinal fluid leak or result from different causes such as a lumbar puncture or physical trauma. 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.

The most common symptoms of a CSFL is extremely high pressure in the head when sitting, standing, or bending down which can be lessened by laying down flat.

A myelogram can be used to help identify a CSFL by injecting a dye to further enhance the imaging allowing the location of the leak to be found. If it is a slow leak it may not appear on a single myelogram so more than one may be needed. Due to the ease of the procedure no anesthesia is used however a local anesthetic is given.

An epidural blood patch is the normal treatment for a CSFL, the patient's blood is drawn and it is then injected into the lumbar spine. Patients are told to lie flat without moving from 2 to 24 hours after the blood patch is done. A blood patch can be used to patch a CSFL in the cervical neck although it is rare for it to be done in that location, though it may take more than one blood patch to fully close the leak. Anesthesia is also uncommon for blood patch procedures. If you have a low pain tolerance it would be a good idea to have anesthesia for all of the procedures.

If the leak is strong or fast, the loss of CSF fluid can cause the brain to drop inside the skull due to the body's inability to replenish the CSF fluid at a quick enough pace, which would show up on a MRI of the brain. This is called a Chiari malformation where the brain is lower in the skull almost in the spinal canal.

The original criteria for IIH were described by Dandy in 1937.

They were modified by Smith in 1985 to become the "modified Dandy criteria". Smith included the use of more advanced imaging: Dandy had required ventriculography, but Smith replaced this with computed tomography. In a 2001 paper, Digre and Corbett amended Dandy's criteria further. They added the requirement that the patient is awake and alert, as coma precludes adequate neurological assessment, and require exclusion of venous sinus thrombosis as an underlying cause. Furthermore, they added the requirement that no other cause for the raised ICP is found.

In a 2002 review, Friedman and Jacobson propose an alternative set of criteria, derived from Smith's. These require the absence of symptoms that could not be explained by a diagnosis of IIH, but do not require the actual presence of any symptoms (such as headache) attributable to IIH. These criteria also require that the lumbar puncture is performed with patient lying sideways, as a lumbar puncture performed in the upright sitting position can lead to artificially high pressure measurements. Friedman and Jacobson also do not insist on MR venography for every patient; rather, this is only required in atypical cases (see "diagnosis" above).

Many laboratories rely on only the color of the cerebrospinal fluid to determine the presence or absence of xanthochromia. However, recent guidelines suggest that spectrophotometry should be performed. Spectrophotometry relies on the different transmittance, or conversely, absorbance, of light by different substances or materials, including solutes. Bilirubin absorbs light at wavelengths between 450–460 nm. Spectrophotometry can also detect the presence of oxyhemoglobin and methemoglobin, which absorb light at 410-418 nm and 403-410 nm, respectively, and also may indicate that bleeding has occurred; to identify substances in cerebrospinal fluid that absorb light at other wavelengths but are not due to bleeding, such as carotenoids; and to detect very small amounts of yellow color saturation (about 0.62%) which may be missed by visual inspection, especially when the cerebrospinal fluid has been examined under incandescent lighting or a tungsten desk lamp (corresponding to International Commission on Illumination standard illuminant A).

Visual inspection is the most frequent method used in the United States to assess cerebrospinal fluid for xanthochromia, while spectrophotometry is used on up to 94% of specimens in the United Kingdom. There is still disagreement about whether or not to routinely use spectrophotometry or whether visual inspection is adequate, and one group of authors has even advocated measuring bilirubin levels.

Diagnosis is principally by MRI. Frequently, arachnoid cysts are incidental findings on MRI scans performed for other clinical reasons. In practice, diagnosis of symptomatic arachnoid cysts requires symptoms to be present, and many with the disorder never develop symptoms.

Additional clinical assessment tools that can be useful in evaluating a patient with arachnoid cysts include the mini-mental state examination (MMSE), a brief questionnaire-based test used to assess cognition.

Lumbar puncture, in which cerebrospinal fluid (CSF) is removed from the subarachnoid space of the spinal canal using a hypodermic needle, shows evidence of hemorrhage in 3 percent of people in whom CT was found normal; lumbar puncture is therefore regarded as mandatory in people with suspected SAH if imaging is negative. At least three tubes of CSF are collected. If an elevated number of red blood cells is present equally in all bottles, this indicates a subarachnoid hemorrhage. If the number of cells decreases per bottle, it is more likely that it is due to damage to a small blood vessel during the procedure (known as a "traumatic tap"). While there is no official cutoff for red blood cells in the CSF no documented cases have occurred at less than "a few hundred cells" per high-powered field.

The CSF sample is also examined for xanthochromia—the yellow appearance of centrifugated fluid. This can be determined by spectrophotometry (measuring the absorption of particular wavelengths of light) or visual examination. It is unclear which method is superior. Xanthochromia remains a reliable ways to detect SAH several days after the onset of headache. An interval of at least 12 hours between the onset of the headache and lumbar puncture is required, as it takes several hours for the hemoglobin from the red blood cells to be metabolized into bilirubin.

The modality of choice is computed tomography (CT scan) without contrast, of the brain. This has a high sensitivity and will correctly identify over 95 percent of cases—especially on the first day after the onset of bleeding. Magnetic resonance imaging (MRI) may be more sensitive than CT after several days. Within six hours of the onset of symptoms CT picks up 98.7% of cases.

The most important initial investigation is computed tomography of the brain, which is very sensitive for subarachnoid hemorrhage. If this is normal, a lumbar puncture is performed, as a small proportion of SAH is missed on CT and can still be detected as xanthochromia.

If both investigations are normal, the specific description of the headache and the presence of other abnormalities may prompt further tests, usually involving magnetic resonance imaging (MRI). Magnetic resonance angiography (MRA) may be useful in identifying problems with the arteries (such as dissection), and magnetic resonance venography (MRV) identifies venous thrombosis. It is not usually necessary to proceed to cerebral angiography, a more precise but invasive investigation of the brain's blood vessels, if MRA and MRV are normal.

A computed tomography (CT) scan is another examination method often used for the diagnosis of Tarlov cyst. Unenhanced CT scans may show sacral erosion, asymmetric epidural fat distribution, and cystic masses that are have the same density with CSF. CT Myelogram is minimally invasive, and could be employed when MRI cannot be performed on patient.

Two most commonly used and effective examination method for Tarlov Cysts are MRI and CT. Both CT and MRI are good imaging procedures that allow the detection of extradural spinal masses such as Tarlov cysts. Magnetic resonance neurography is an emerging imaging technology based on MRI that highlights neurologic tissue. Often cysts are under reported and under diagnosed as radiologists and neurosurgeons have been traditionally taught to ignore these cysts. Patients frequently experience difficulty in diagnosis, however this is changing as Tarlov cysts have now been recognized by NORD as a rare disease.

Most arachnoid cysts are asymptomatic, and do not require treatment. Where complications are present, leaving arachnoid cysts untreated, may cause permanent severe neurological damage due to the progressive expansion of the cyst(s) or hemorrhage (bleeding). However, with treatment most individuals with symptomatic arachnoid cysts do well.

More specific prognoses are listed below:

- Patients with impaired preoperative cognition had postoperative improvement after surgical decompression of the cyst.

- Surgery can resolve psychiatric manifestations in selected cases.

It is important that a person receive medical assessment, including a complete neurological examination, after any head trauma. A CT scan or MRI scan will usually detect significant subdural hematomas.

Subdural hematomas occur most often around the tops and sides of the frontal and parietal lobes. They also occur in the posterior cranial fossa, and near the falx cerebri and tentorium cerebelli. Unlike epidural hematomas, which cannot expand past the sutures of the skull, subdural hematomas can expand along the inside of the skull, creating a concave shape that follows the curve of the brain, stopping only at the dural reflections like the tentorium cerebelli and falx cerebri.

On a CT scan, subdural hematomas are classically crescent-shaped, with a concave surface away from the skull. However, they can have a convex appearance, especially in the early stage of bleeding. This may cause difficulty in distinguishing between subdural and epidural hemorrhages. A more reliable indicator of subdural hemorrhage is its involvement of a larger portion of the cerebral hemisphere since it can cross suture lines, unlike an epidural hemorrhage. Subdural blood can also be seen as a layering density along the tentorium cerebelli. This can be a chronic, stable process, since the feeding system is low-pressure. In such cases, subtle signs of bleeding such as effacement of sulci or medial displacement of the junction between gray matter and white matter may be apparent. A chronic bleed can be the same density as brain tissue (called isodense to brain), meaning that it will show up on CT scan as the same shade as brain tissue, potentially obscuring the finding.

The clinician should first rule out conditions with similar symptoms, such as subarachnoid hemorrhage, ischemic stroke, pituitary apoplexy, cerebral artery dissection, meningitis, and spontaneous cerebrospinal fluid leak. This may involve a CT scan, lumbar puncture, MRI, and other tests. Posterior reversible encephalopathy syndrome has a similar presentation, and is found in 10–38% of RCVS patients.

RCVS is diagnosed by detecting diffuse reversible cerebral vasoconstriction. Catheter angiography is ideal, but computed tomography angiography and magnetic resonance angiography can identify about 70% of cases. Multiple angiographies may be necessary. Because other diseases (such as atherosclerosis) have similar angiographic presentations, it can only be conclusively diagnosed if vasoconstriction resolves within 12 weeks.

Physicians now use magnetic resonance imaging (MRI) to diagnose syringomyelia. The MRI radiographer takes images of body anatomy, such as the brain and spinal cord, in vivid detail. This test will show the syrinx in the spine or any other conditions, such as the presence of a tumor. MRI is safe, painless, and informative and has greatly improved the diagnosis of syringomyelia.

The physician may order additional tests to help confirm the diagnosis. One of these is called electromyography (EMG), which show possible lower motor neuron damage. In addition, computed axial tomography (CT) scans of a patient's head may reveal the presence of tumors and other abnormalities such as hydrocephalus.

Like MRI and CT scans, another test, called a myelogram, uses radiographs and requires a contrast medium to be injected into the subarachnoid space. Since the introduction of MRI this test is rarely necessary to diagnose syringomyelia.

The possible causes are trauma, tumors and congenital defects. It is most usually observed in the part of the spinal cord corresponding to the neck area. Symptoms are due to spinal cord damage and are: pain, decreased sensation of touch, weakness and loss of muscle tissue. The diagnosis is confirmed with a spinal CT, myelogram or MRI of the spinal cord. The cavity may be reduced by surgical decompression.

Furthermore, evidence also suggests that impact injuries to the thorax area highly correlate with the occurrence of a cervical-located syrinx.

Froin's syndrome – coexistence of xanthochromia, high protein level and marked coagulation of cerebrospinal fluid (CSF). It is caused by meningeal irritation (e.g. during spinal meningitis) and CSF flow blockage by tumour mass or abscess. Stagnation of the CSF within the thecal sac facilitates exudation from the tumour itself and activation of coagulation factors. A clinical test formerly used for evaluation of spinal stenosis is Queckenstedt's maneuver. Nowadays, a magnetic resonance imaging is used for identification of CSF flow obstruction. It often shows the prolongation of T1 and T2 signal in CSF caudal to a level of block. This phenomenon is named after Georges Froin (1874–1932), a French physician who first described it.

Cerebrospinal fluid, which fills the subarachnoid space between the arachnoid membrane and the pia mater surrounding the brain, is normally clear and colorless. When there has been bleeding into the subarachnoid space, the initial appearance of the cerebrospinal fluid can range from barely tinged with blood to frankly bloody, depending on the extent of bleeding. Within several hours, the red blood cells in the cerebrospinal fluid are destroyed, releasing their oxygen-carrying molecule heme, which is then metabolized by enzymes to bilirubin, a yellow pigment. The most common cause for bleeding into the subarachnoid space is a subarachnoid hemorrhage from a ruptured cerebral aneurysm.

The most frequently employed initial test for subarachnoid hemorrhage is a computed tomography scan of the head, but it detects only 98% of cases in the first 12 hours after the onset of symptoms, and becomes less useful afterwards. Therefore, a lumbar puncture ("spinal tap") is recommended to obtain cerebrospinal fluid if someone has symptoms of a subarachnoid hemorrhage (e.g., a thunderclap headache, vomiting, dizziness, new-onset seizures, confusion, a decreased level of consciousness or coma, neck stiffness or other signs of meningismus, and signs of sudden elevated intracranial pressure), but no blood is visible on the CT scan. According to one article, a spinal tap is not necessary if no blood is seen on a CT scan done using a third generation scanner within six hours of the onset of the symptoms. However, this is not standard of care.

Heme from red blood cells that are in the cerebrospinal fluid because a blood vessel was nicked during the lumbar puncture (a "traumatic tap") has no time to be metabolized, and therefore no bilirubin is present.

After the cerebrospinal fluid is obtained, a variety of its parameters can be checked, including the presence of xanthochromia. If the cerebrospinal fluid is bloody, it is centrifuged to determine its color.

Treatment of a subdural hematoma depends on its size and rate of growth. Some small subdural hematomas can be managed by careful monitoring until the body heals itself. Other small subdural hematomas can be managed by inserting a temporary small catheter through a hole drilled through the skull and sucking out the hematoma; this procedure can be done at the bedside. Large or symptomatic hematomas require a craniotomy, the surgical opening of the skull. A surgeon then opens the dura, removes the blood clot with suction or irrigation, and identifies and controls sites of bleeding. Postoperative complications include increased intracranial pressure, brain edema, new or recurrent bleeding, infection, and seizure. The injured vessels must be repaired.

Depending on the size and deterioration, age of the patient, and anaesthetic risk posed, subdural hematomas occasionally require craniotomy for evacuation; most frequently, simple burr holes for drainage; often conservative treatment; and rarely, palliative treatment in patients of extreme age or with no chance of recovery.

In those with a chronic subdural hematoma, but without a history of seizures, the evidence is unclear if using anticonvulsants is harmful or beneficial.

A pseudomeningocele is an abnormal collection of cerebrospinal fluid (CSF) that communicates with the CSF space around the brain or spinal cord. In contrast to a meningocele, in which the fluid is surrounded and confined by dura mater, in a pseudomeningocele, the fluid has no surrounding membrane, but is contained in a cavity within the soft tissues.

Pseudomeningocele may result after brain surgery, spine surgery, or brachial plexus avulsion injury.

Treatment for pseudomeningocele is conservative or may involve neurosurgical repair.

As of 2014, no treatment strategy has yet been investigated in a randomized clinical trial. Verapamil, nimodipine, and other calcium channel blockers may help reduce the intensity and frequency of the headaches. A clinician may recommend rest and the avoidance of activities or vasoactive drugs which trigger symptoms (see § Causes). Analgesics and anticonvulsants can help manage pain and seizures, respectively.

Whole spine MR imaging may be used to evaluate the extent of syrinx formation (fluid filled cavity within the spinal cord) in CM dogs, developing a thermal camera-based screening test for the disorder and a method of measuring the actual syrinx volume from MR images.

Before the introduction of MRI, the diagnosis of CM and SM were commonly confused with that of allergic skin disorders, disk disease, ear infections and epilepsy. After CM was reported in human patients, the initial research was provided for the diagnosis of animals. MRI in animals is safe, however, to ensure that the patient remains motionless, light general anesthesia is required.

According to recent studies, thermography may be a useful tool in the diagnosis of CM and SM. Thermography requires no sedation or clipping of hair for a dog to be imaged by the infrared camera. After the image is captured, computer software is used to assess changes in the temperature and color pattern to detect abnormality.

The precise causes of syringomyelia are still unknown although blockage to the flow of cerebrospinal fluid has been known to be an important factor since the 1970s. Scientists in the UK and America continue to explore the mechanisms that lead to the formation of syrinxes in the spinal cord. It has been demonstrated a block to the free flow of cerebrospinal fluid is a contributory factor in the pathogenesis of the disease. Duke University in America and Warwick University are conducting research to explore genetic features of syringomyelia.

Surgical techniques are also being refined by the neurosurgical research community. Successful procedures expand the area around the cerebellum and spinal cord, thus improving the flow of cerebrospinal fluid thereby reducing the syrinx.

It is also important to understand the role of birth defects in the development of hindbrain malformations that can lead to syringomyelia as syringomyelia is a feature of intrauterine life and is also associated with spina bifida. Learning when these defects occur during the development of the fetus can help us understand this and similar disorders, and may lead to preventive treatment that can stop the formation of some birth abnormalities. Dietary supplements of folic acid prior to pregnancy have been found to reduce the number of cases of spina bifida and are also implicated in prevention of cleft palate and some cardiac defects.

Diagnostic technology is another area for continued research. MRI has enabled scientists to see conditions in the spine, including syringomyelia before symptoms appear. A new technology, known as dynamic MRI, allows investigators to view spinal fluid flow within the syrinx. CT scans allow physicians to see abnormalities in the brain, and other diagnostic tests have also improved greatly with the availability of new, non-toxic, contrast dyes.

Although surgery is the treatment of choice, it must be preceded by imaging studies to exclude an intracranial connection. Potential complications include meningitis and a cerebrospinal fluid leak. Recurrences or more correctly persistence may be seen in up to 30% of patients if not completely excised.

Imaging studies are performed before surgery or biopsy to preclude an intracranial connection. Images usually show a sharply circumscribed but expansile mass. It may be difficult to exclude the intracranial connection if the defect is small whether employing computed tomography or magnetic resonnance.