Musician Abhishek Prasad strummed his guitar throughout his neurosurgery to help doctors zero in on the part of his brain being operated on during the first such procedure in India.
The 37-year-old had been suffering from musician’s dystonia, a neurological movement disorder which leads to involuntary muscle contractions. Focal dystonia is a neurological condition, a type of dystonia, that affects a muscle or group of muscles in a specific part of the body, causing involuntary muscular contractions and abnormal postures. For example, in focal hand dystonia, the fingers either curl into the palm or extend outward without control. In musicians, the condition is called musician’s focal dystonia, or simply, musician’s dystonia. In sports, it is commonly referred to as the yips.
Current medical science does not precisely describe the causes of dystonia. Misfiring of neurons in the sensorimotor cortex, a thin layer of neural tissue that covers the brain, is thought to cause contractions. This misfiring may result from impaired inhibitory mechanisms during muscle contraction. When the brain tells a given muscle to contract, it simultaneously silences muscles that would oppose the intended movement. It appears that dystonia interferes with the brain’s ability to inhibit those surrounding muscles, leading to loss of selectivity.
The sensorimotor cortex is organized as discrete “maps” of the human body. Under normal conditions, each body part (such as individual fingers) occupies a distinct area on these cortical maps. In dystonia, these maps lose their distinct borders and overlap occurs. Exploration of this initially involved over-training particular finger movements in non-human primates, which resulted in the development of focal hand dystonia. Examination of the primary somatosensory cortex in the trained animals showed grossly distorted representations of the maps pertaining to the fingers when compared to the untrained animals. Additionally, these maps in the dystonic animals had lost the distinct borders that were noted in the untrained animals.
Imaging studies in humans with focal dystonia have confirmed this finding. Also, synchronous afferent stimulation of peripheral muscles induces organizational changes in motor representations, characterized both by an increase in map size of stimulated muscles and a reduction in map separation, as assessed using transcranial magnetic stimulation.
The cross-connectivity between areas that are normally segregated in the sensory cortex may prevent normal sensorimotor feedback and so contribute to the observed co-contraction of antagonist muscle groups, and inappropriately timed and sequenced movements that underlie the symptoms of focal dystonia. It is hypothesized that a deficit in inhibition caused by a genetically mediated loss of inhibitory interneurons may be the underlying cause of the deficits observed in dystonia.
While usually painless, in some instances the sustained contraction and abnormal posturing in dystonia cause pain. Focal dystonia most typically affects people who rely on fine motor skills—musicians, writers, surgeons, etc. It is thought that the excessive motor training those skills require may contribute to the development of dystonia as their cortical maps become enlarged and begin to overlap. Focal dystonia is generally “task-specific,” meaning that it is only problematic during certain activities.
Mr Prasad had to be kept conscious during the seven-hour operation as the doctors needed continuous feedback to work out exactly which parts of the brain were to be targeted to stop the cramps affecting the three fingers on his left hand.
It is only the eighth time in the world that such a procedure has been undertaken with the patient being conscious.
“A 14mm hole was made in the skull and a specialized electrode was passed into the brain under local anesthesia,” Sharan Srinivasan, a stereotactic and functional neurosurgeon at the hospital, said. Mr Prasad was overwhelmed with the outcome after living since October 2015 with the disorder that could have ended his career. After the surgery he needed a couple of weeks of physiotherapy to help his recovery and get back to performing pain-free.
Thank you to Doctor ZG for part of this article – www.Instagram.com/Doctor.ZG