Adcock is suffering from essential tremor, a progressive neurological condition characterised by tremors in the arms which appear during voluntary movements and which are thought to occur as a result of degeneration of cerebellar Purkinje cells.
The film shows neurosurgeons at Vanderbilt University Medical Center in Nashville, Tennessee treating Adcock with deep brain stimulation (DBS), in which electrodes are implanted into the thalamus. Together with the cerebellum and cerebral cortex, the thalamus forms a circuit that controls movement.
DBS is still an experimental procedure, but it has been used successfully as a treatment for essential tremor since 1997, and for Parkinson’s Disease, which has similar but far more severe symptoms, since 2002.
In this case, the surgeons used the banjo to fine tune the treatment. Because of his tremors, Adcock no longer had the dexterity required for his characteristic fast picking style. He played the instrument during his operation so that the surgeons could pinpoint exactly where the electrodes would be most effective.