DIAGNOSIS

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"Listen to your patient; he is telling you the diagnosis."-William Osler

Under-diagnosis and/or misdiagnosis of a spinal CSF leak/ Spontaneous intracranial hypotension (SIH) is extremely common, resulting in little or no treatment for some patients suffering from it. Currently, there is not a single diagnostic test that can rule out SIH with a high degree of certainty; therefore, detailed assessment and investigation of symptoms by a specialist is crucial. 

Symptoms

Experts agree that symptoms and history of the patient are extremely important for a successful diagnosis: see SYMPTOMS.

48 Hour Flat Test 

Dr. Carroll has devised a 48 hour Flat Test to assist physicians in determining the extent to which a patient’s headache has a postural component through which symptoms improve or worsen in response to body position (horizontal vs vertical).

Imaging 

Some patients with spinal CSF leaks may require a few scans to diagnose a leak, while others require several different types of tests or repeated testing over time to establish the diagnosis.

There is no diagnostic imaging test that is 100% accurate in determining whether someone is leaking.  It is important to note that imaging of patients with spinal CSF leaks may sometimes be normal, and an MRI is not solely adequate in diagnosing a spinal CSF leak. Spinal CSF leaks can exist without any evidence of a leak on imaging. A negative MRI of the brain or spine does not rule out a spinal CSF leak. Even when positive for a CSF leak, current spinal imaging is not always adequate for locating all leaks.  Symptoms are usually key in diagnosing a leak, as noted above. 

In addition, interpretation of imaging requires experience and training.

Different types of imaging include: 

  • Brain MRI (with and without contrast) should be done in all cases where a spinal CSF leak is suspected. 

There are 5 brain abnormalities remembered by the acronym SEEPS, that can be found on an MRI of the brain:

Subdural fluid collections
Enhancement of pachymeninges (also known as dural enhancement)
Engorgement of venous structures
Pituitary hyperemia
Sagging of the brain

The brain (Bern) SIH-Score (bSIH-Score) is a quantitive scoring system of cranial MRI used to indicate the likelihood of identifying a CSF leak during more specialized spinal imaging. This scoring system relies on the six most pertinent brain MRI findings (with three major factors assigned 2 points each (pachymeningeal enhancement, venous sinus engorgement, and effacement of the suprasellar cistern ≤ 4.0 mm) and three minor factors given 1 point each (subdural fluid collection, effacement of the prepontine cistern ≤ 5.0 mm, and mamillopontine distance ≤ 6.5 mm), enabling an evaluation of the probability of a positive spinal imaging outcome in individuals with SIH ranging from 0 to 9 (higher values are associated with higher possibilities of finding a CSF leak). However, if the Bern Score suggests a low probability, patients should not be deprived of necessary evaluation and treatment if clinical suspicion remains significantly elevated.

  • A Full Spinal MRI  (Cervical, Thoracic, Lumbar) with and without contrast 

Some of the most common abnormalities that can be found suggesting possible CSF leakage through a full spinal MRI are: fluid collections, collapse of the dural sac and irregular root sleeves.

  • CT/MR Myelography

MR myelography is a specialized non-invasive MRI that does not rely on the injection of contrast to view the spine.  Sometimes, it can be sufficient to localize a leak and further invasive testing is not required.

If invasive testing is required however, CT myelography is the study of choice for locating a leak once spinal a CSF leak is suspected.  This procedure is superior in locating fast or slow-flow leaks, but does involve injection of contrast dye into the spinal area. It also uses radiation, whereas an MRI does not involve any radiation

  • Digital Subtraction Myelogram (“DSM”)

If a large or fast leak, or CSF Venous Fistulas are suspected, and CT/MR myelography fails to locate the site of the leak(s), a DSM may help to locate the leak. 

Non-targeted Epidural Blood Patch (EBP) 

Sustained improvement of symptoms after epidural blood patching is a good indication of a spinal CSF leak. This type of patch is referred to as a “blind” or ”non-targeted” or “non-directed” epidural blood patch (EBP) because the procedure involves the injection of the patient’s own blood into the spinal epidural space without knowledge of the level of the site of the leak.  Experts believe that, through this approach, the clotting factors in the blood can seal the leak.

If the initial non-targeted EBP is unsuccessful, a second, larger-volume EBP is sometimes considered, and some recommend a third lumbar or even lower thoracic level EBP before proceeding with localization of the leak with more invasive testing (i.e.: CT Myelography). However, a blood patch is more effective if directed to the site of the identified leak.

Neurological and Physical Examination

The results of a neurological examination are usually normal, but may show some signs related to the neurological symptoms caused by a CSF leak.  These signs can vary but can include cognitive, visual, sensory, motor, balance and walking problems.

Other Diagnostic Tools– rarely recommended or required:

Radioisotope Cisternogram – Rarely used in current practice.

Lumbar Puncture – CSF opening pressure 

A Lumbar puncture is not a helpful diagnostic tool and is not required to make a diagnosis. The risks of the procedure outweigh its benefits. While low CSF opening pressure was once thought to be the defining characteristic of the condition, experts now believe that Intracranial Hypotension is predominantly due to low CSF volume, rather than low CSF pressure. The majority of patients with SIH exhibit opening CSF pressures within the normal range. A normal opening pressure does not exclude the diagnosis.

Blood Work

Blood work is usually normal in patients with CSF leaks.  There is currently no routine diagnostic test on blood work for spinal CSF leaks.

Possible Misdiagnosis

A CSF leak is often misdiagnosed as one of the following conditions:

  • Chronic migraine 

  • Chronic tension type headache

  • Chiari malformation 1

  • Postural orthostatic tachycardia syndrome (POTS)

  • Dementia (in some very rare cases)

  • Cervicogenic headache

  • New daily persistant headache (NDPH)

Key Notes

  • Before and during testing it is helpful to perform provocative maneuvers such as coughing and staying in an upright position.

  • It is a myth and a misconception that a negative brain MRI excludes the possibility of SIH. 

  • About 15-20% of patients with spinal CSF leak(s) have normal MRI brain imaging.

  • There is a need for higher resolution imaging able to detect leaks that cannot be detected with traditional testing. 

  • There is a need for less invasive diagnostic techniques. 

  • A negative MRI does not rule out a spinal CSF leak but a positive MRI does rule in a spinal CSF leak.

  • Opening pressure (OP) is not an effective predictor for diagnosing spinal CSF leak s and if used in isolation would result in misdiagnosis. OP can, in fact, be normal or even elevated, particularly in patients with chronic SIH.

  • For any imaging requiring a lumbar puncture, a smaller size needle and an expert radiologist can minimize the risk of creating further spinal CSF leaks during testing.

  • Imaging is a helpful and often critical part of identifying suspicious findings that dictate where a blood patch should be directed rather than telling if a leak is present.

  • Occasionally, patients will be leaking from more than one location.

  • An elevated level of prolactin can indicate a spinal CSF leak when other symptoms are present.

Sources & Suggested Reading