Description of the Disease and its Symptoms
Parkinson’s disease (PD) is a disorder associated with the degeneration of the nervous system. It is caused by multiple factors including genetic and environmental factors. Some of the symptoms of PD include difficulty in writing well, blurred speech, difficulty in performing automatic movement (such as swinging one’s arms), stooped posture and impaired balance, stiff muscles, shaking of the hands when relaxed and slow movement (Schapira, 2010). Tremor (shaking of the hands, arms, or legs when relaxed) is the first symptom that most patients notice. Problem with walking then develops, as the patient is unable to maintain body balance and posture. In the later stages of the disease, the patient may have trouble when performing simple movement because the muscles are stiff.
Causes
According to Schapira (2010), “a number of disease-causing genes have been identified in both familial and sporadic forms of PD.” This means that the disease may be hereditary. For people with PD because of familial associations, this occurs because the disease-causing genes are passed from one generation to another. Those family members share mutation in a specific gene. Mutation leads to an error in the development of a particular protein that influences the brain. In some families, it has been found that mutation occurs in a protein known as alpha-synuclein, where there is a change in the protein’s amino acid composition (Sharma & Richman, Cambridge, MA). In other families, the mutation has been found in a protein called parkin (Sharma & Richman, Cambridge, MA). Environmental factors increase the risk of PD. The environment modulates the risk of the disease (Schapira, 2010). For instance, it is believed that PD was prevalent during the industrial revolution because of the pollutants released into the air (Sharma & Richman, Cambridge, MA). The use of a chemical called MPTP found in heroin also been linked with PD. The use of pesticides and herbicides has also been linked to PD (Sharma & Richman, Cambridge, MA).
Parts of the Brain Affected
The symptoms of PD manifest themselves after the deterioration of nervous cells in a brain area called substantia nigra. The substantia nigra is found in a part of the brain known as basal ganglia. The area controls body balance, posture, and movement (Lieberman, 2010). Nervous cells found in the substantia nigra produce a chemical called dopamine. The chemical is crucial in mediating communication between the substantia nigra and other areas of the brain. The communication facilitates smooth movement of the muscles. When those nerve cells are impaired such that they cannot produce dopamine, the normal functioning of the nerve cells is impaired, leading to the inability to control movement of the body. In severe cases, PD may affect the cortex, which is responsible for memory and thinking (Lieberman, 2010). For this reason, people with PD may experience loss of memory.
Why the Neurologist Prescribed Selegiline and L-dopa
The neurologist prescribed L-dopa because it treats dopamine deficiency. After taking L-dopa orally, some of it goes to the brain where it is converted into dopamine. The net effect is that the patient experiences temporary relief of PD symptoms. L-dopa has proved to be effective thus far, and this is the reason the neurologist prescribed it for the patient (Ebadi, 2010). Selegiline on the other hand “prolongs the action of L-dopa” and increases the life expectancy of the patient (Ebadi, 2010). It works by inhibiting the breakdown of dopamine, thus compensating for its diminished production. Studies have shown that Selegiline slows down the progression of PD, thus delaying the requirement for antiparkinsonian medications (Ebadi, 2010).
Most Likely Disorder for the Surgery Performed and how the Surgery is Performed
The patient could be suffering from epilepsy. The surgery performed, corpus callosotomy, is meant for the corpus callosum, an area of the brain that connects the two brain hemispheres (the right hemisphere and the left hemisphere). Corpus callosum facilitates the sharing of information between the two hemispheres. It also facilitates the spread of seizures from one hemisphere to the other. The corpus callosotomy surgery cuts the corpus callosum, thus preventing the spread of seizures from one part of the hemisphere to the other.
How the surgery is expected to help Sabrina
After the corpus callosum is severed, seizures cannot spread from one hemisphere to the other. For this reason, it is highly likely that Sabrina experiences less severe seizures.
Benefits and Risks
One of the benefits of corpus callosotomy is that it reduces seizures. In some patients, corpus callosotomy reduces seizures by 56-100% (Nordgren, 2013). In young patients, corpus callosotomy may improve behavior and alertness (Nordgren, 2013). However, it should be noted that corpus callosotomy does stop the seizures completely; it only contains the seizures to one hemisphere thus the patient cannot experience severe seizures. Some of the risks associated with corpus callosotomy include death, stroke, excessive bleeding of the brain, increased partial seizures, loss of the ability to coordinate brain functions well and blurred speech.
One of the alternatives to corpus callosotomy is vagal nerve stimulator (VNS). It is more beneficial compared to corpus callosotomy because of low morbidity. Risks associated with VNS include lack of empirical research supporting the efficacy of VNS in the long term and significant maintenance costs that make it more costly when compared to corpus callosotomy (Guthikonda, Smitherman, & Yoshor, 2009).
Given the scenario of Sabrina, I would recommend the use of VNS because the chances of survival as great compared to the use of corpus callosotomy. In addition, VNS is less likely to affect coordination and other brain processes.
Cause of Apraxia
For the patients who have had corpus callosotomy performed on them, it is normal to experience difficulties “naming aloud objects felt with the left hand” and the “inability to execute with the left-hand actions described by the examiner” (Bogen, 2013). This occurs due to the severing of the corpus callosum through which information flows. Corpus callosum is particularly crucial in the execution of left-hand responses to verbal commands. Under normal circumstances, verbal instructions to be performed by the left hand are understood by the left hemisphere of the brain but controlled by the right hemisphere (Bogen, 2013). Therefore, the corpus callosum is important in facilitating the transfer of communication from the left hemisphere to the right hemisphere to enable the right hemisphere control the actions of the left hand. However, the apraxia “recedes in a few months” (Bogen, 2013).
What reduction of Apraxia Indicates about Hemispheric Specialization
The case of Sabrina shows that while the right and left hemispheres of the brain have distinct functions, the brain can still adjust to brain damage. Some functions of the brain performed by the damaged part are taken over by other parts of the brain, thus the brain compensates for the damaged part by assigning other parts of the brain to those functions. However, the brain takes time to adjust in adults as compared to children.
References
Bogen, J. (2013). Some historical aspects of callosotomy for epilepsy. In A. G. Reeves, & D. W. Roberts, Epilepsy and the corpus 2 callosum (pp. 107-111). New York, NY: Springer.
Ebadi, M. (2010). Pharmacodynamic basis of herbal medicine. Boca Raton, FL: CRC Press.
Guthikonda, B., Smitherman, S., & Yoshor, D. (2009). Sectioning of the corpus callosum for epilepsy. In P. A. Starr, N. M. Barbaro, & P. S. Larson, Neurosurgical operative atlas: Functional neurosurgery (pp. 67-71). Stuttgart: Thieme.
Lieberman, A. (2010). The Muhammad Ali Parkinson Center 100 Questions & Answers About Parkinson Disease. New York, NY: Jones & Bartlett Learning.
Nordgren, R. (2013). Preoperative operation of children. In A. G. Reeves, & D. W. Roberts, Epilepsy and the Corpus Callosum 2 (pp. 217-220). New York, NY: Springer.
Schapira, A. (2010). Parkinson's Disease. New York, NY: Oxford University Press.
Sharma, N., & Richman, E. (Cambridge, MA). Parkinson's disease and the family: A new guide. 2009: Harvard University Press.
