Cerebrospinal fluid depetion may be caused by a leak or a shunt.
Symptoms commonly include headaches, which are more severe in the upright position and are alleviated by supine positioning. There may also be nausea and tinnitus. Horizontal diplopia, change in hearing, tinnitus, blurring of vision, facial numbness and upper limb radicular symptoms may occur. These symptoms are rather nonspecific as they are commonly encountered in migraine and post-traumatic headache. Cognitive decline has also been reported (Hong et al, 2002; Pleasure et al, 1998).
The leaks are typically at the level of the spine, particularly the thoracic spine and cervicothoracic junction. Sometimes they are unintentional consequences of an overdraining CSF shunt, placed for CSF hypertension. CSF leaks can also occur in the nose after trauma or surgery, and following diagnostic or therapeutic lumbar puncture. Spontaneous leaks from the nose are uncommon (1/26 in Mokri, 1997). Speculatively, it would seem possible that CSF leaks might occur after whiplash injury, as frequently there are persistent similar symptoms without findings on other studies. At this writing however (2002), almost nothing has been published regarding this possibility.
Other conditions to exclude when considering the diagnosis of CSF leak are orthostatic hypotension (which can cause dizziness on standing), positional vertigo due to inner ear disturbances such as BPPV, and orthostatic tremor. When considering leaks from the nose, of course other fluids than CSF can leak out of the nose. "Pseudo-CSF rhinorhea" can occur as a result of injury to the sphenopalatine ganglion (Hilinski et al, 2001).
On lumbar puncture, in approximately half of patients, the opening CSF pressure is 40 mm or less. However, if this is found, one still needs to locate the site of leak. The other half of patients may have normal CSF pressure so a lumbar puncture is not 100% reliable to diagnose low CSF pressure. Of course, there is some danger of causing a leak, per se, with a lumbar puncture, and the risks/benefits must be carefully considered. In a small minority of patients with CSF leak, CSF pressure may be normal although patients continue to have symptoms and abnormal MRI findings. Perhaps this indicates an intermittent situation.
In the past it was thought that CSF could be distinguished from other fluids by it's glucose content. Testing of the fluid dripping from the nose for glucose is no longer thought to be useful. Testing for beta-transferrin may help determine if it is CSF or something else. Another method is to inject radioactive label or a fluorescent dye into the spinal fluid and test for the label or dye in the fluid. Nasal pledgets can be left in the nose for extended periods, enabling detection of intermittent rhinorhea. 0.5 ml of 5% fluorescein diluted in 9.5 cc of CSF is used (according to Hilinski et al, 2001). It is useful to use control pledgets under the upper lip for comparison. the test is analyzed under ultraviolet light. No complications were reported by Montgomery in more than 200 injections of fluorescein.
Radioactive label materials may include technetium or indium 111. Indium is an agent that attaches specifically to CSF proteins. A major disadvantage of the radioactive imaging is high cost and the possibility of false-positive results. This study requires injection of material into the spinal canal.
Radiologic studies are also useful -- contrast cisternography after metrizamide injection is considered to be the most useful during a leak. This may be impractical however if one does not know the level of the leak. Radioisotope cisternography characteristically shows a decrease or absence of activity over the cerebral convexities and early accumulation of radioisotope in the bladder. This study is somewhat invasive, requiring injection of material into the spinal canal.
Head MRI findings include diffuse meningeal gadolinium enhancement due to engorgement of the cerebral venous system (Mokri et al, 1997), imaging evidence of sinking of the brain resembling the Chiari malformation, subdural fluid collection, decrease in ventricular size and prominent dural sinuses. Spine MRI may show extra-arachnoid fluid, meningeal diverticuli, meningeal enhancement, or engorgement of epidural venous plexi. Spinal fluid testing may show a minor pleocytosis of 5 or more cells, and a modest and variable increase in protein (Mokri et al, 1997).
Leaks from the nose can be detected with a new test called beta-trace protein assay (Bachman et al, 2002). It is too soon to say if this test will become widely available and useful.
Treatment may include bed rest, hydration and steroids. Epidural blood patch is used in patients with spinal leaks who fail noninvasive measures. The overwhelming majority of patients have a spinal level leak, although they are generally higher than the lumbar level (Mokri, 1997). Surgical repair may be performed in patients that fail blood patch if the site of the leak has been identified.