Brains and Mysteries

In 2004, my wife suffered a subarachnoid hemorrhage. Numerous MRIs and arteriograms were unable to pinpoint the exact cause or location. A VP shunt was installed due to increasing intracranial pressure. There has been slight short-term memory loss since the event. What is the likelihood of another occurrence and what is the longer-term prognosis?
When angiograms do not find the cause of subarachnoid hemorrhage, that usually means that the chance of a recurrence is very low. Unfortunately, the memory problem could have been caused by damage from the original hemorrhage. Your wife should consult a cognitive and behavioral neurologist about possible treatments.

I heard that there may be a new target for deep brain stimulation (DBS) for patients with progressive supranuclear palsy--the part of the brain called the pedunculopontine. Can you tell me about this target and how DBS would work on it?
Stimulation of the peduculopontine nucleus in the pons is a promising target for deep brain stimulation for people with gait disorders of various kinds. These include Parkinson's disease, syndromes similar to Parkinson's disease and a disease called progressive supranuclear palsy. This form of therapy is still experimental. Deep brain stimulation can work by two separate mechanisms. The first is by stimulating a brain nucleus so rapidly that it cannot recover between stimuli, thus simulating a destructive lesion. It was discovered many years ago that the biochemical changes of Parkinson's disease result in overactivity of certain nuclei in the brain, particularly the globus pallidus and the subthalamic nuclei. The first surgical treatments for Parkinson's disease involved destroying these structures, thereby reducing the overactivity. This is less than optimal therapy: destroying brain structures can lead to some unavoidable side effects. By stimulating these structures very rapidly, their overactivity is reduced but they are not destroyed. This allows the doctors to turn off the stimulator or even remove the stimulating electrodes if the treatment does not work or is causing unacceptable side effects. As far as we know, most deep brain stimulation works by this mechanism. It is also possible that one could use the stimulator to make an abnormally silent structure become active. As of this moment, the precise mechanism of deep brain stimulation in the pons to restore gait has not been discovered. But it could be this "activation" effect.

Samuels is neurologist-in-chief at Brigham and Women's Hospital and professor of neurology at Harvard Medical School. For more information go to health.harvard.edu. Readers should consult a medical professional for an accurate diagnosis.

© 2007