Specific Imaging Findings

MRI using T2-weighted sequences is the imaging method of choice, particularly with gradient-recalled echo T2* techniques. Susceptibility effects induced by superficial siderosis (SS) are more obvious at 3.0 T than at 1.5 T. A black line follows the contour of the cerebellum, medulla, pons, and midbrain and to a lesser extent the supratentorial regions such as the temporal lobes (particularly the sylvian and interhemispheric fissures). The cisternal portions of the cranial nerves may also appear dark. The surface of the spinal cord can also show SS. The cerebellum commonly shows atrophy particularly in its vermis and the anterior aspects of the hemispheres. The cerebral hemispheres may also be atrophic. Occasionally, dystrophic calcifications develop in areas of chronic SS, which is better seen on CT. Contrast enhancement may rarely occur. The most important role of imaging is to look for the underlying cause of SS. If the brain study does not reveal obvious causes the next step is spinal MRI. If all MRI studies are non-conclusive a myelogram and post-myelogram CT may be done to identify causes of CSF leak in spinal axis. Occasionally cerebral and spinal angiography may be used as the last resort in attempting to find out the reason for SS.

Pertinent Clinical Information

Classically, SS presents in adults with progressive gait ataxia and other cerebellar abnormalities as well as sensorineural hearing loss and other cranial nerve deficits. Pyramidal signs and loss of bladder control are observed in a small number of patients and at the end of the disease, dementia will develop in about 25% of patients. SS should be excluded in all patients with signs of cerebellar degeneration. CSF analysis may reveal xanthochromia, high iron concentrations, red blood cells and increased proteins. The peripheral nervous system is not affected but involvement of spinal nerve roots may give rise to conflicting clinical symptoms.