Movement Disorders
1ST A bit of info on the framework of movement !
The motor cortex
The motor cortex is one area of the brain which is most involved with controlling voluntary movements. The motor cortex is located in the back portion of the frontal lobe.The motor cortex is divided into two main areas. the primary motor cortex and the somatiosensory cortex. For voluntary movement to be carried out the motor cortex must 1st receive information about the bodys position in space from the parietal lobe about the movement that needs to achieved and the appropriate method for attaining it, from the anterior portion of the frontal lobe about memories of previous strategies.
Basal Ganglia
The basal ganglia is found deep inside the cerebum the main areas of the basal ganglia are the caudate nucleus, the putamen, and the globus pallidus.These are clusters of nerve cella which are interconnnected tightly they receive information from several different regions of the cerebral cortex. Once the basal ganglia collects and processes this info the send it to the motor cortex through the thalamus.
This diagram below shows the system of communication in the brain
In addition, to ensure that all of these movements are fast, precise, and co-ordinated, the nervous system must constantly receive sensory information from the outside world and use this information to adjust and correct the hand's trajectory. The nervous system achieves these adjustments chiefly by means of the cerebellum, which receives information about the positions in space of the joints and the body from the proprioceptors.
Parkinsons disease
Parkinsons disease affects the way in which the brain co-ordinates body movements inlcuding walking talking and writing.
The cause of parkinsons disease is a chronic degenrative disorder of the parts of the brain that control motor system and manifests with progressive loss of the abiklity to co ordinate movements. This happens when the loss of nerve cells In the area of the brain called the substantia Nigra of the mid brain area (controls movement) dies or suffers from some damage. Because of these dying cells the chemical messenger dopamine is no longer sufficent in the amount that is produced and so the onset of sympotms such as a resting tremor, slowness in initiating movement and muscle stiffness can occur. This causes movement does not work so well and causes it to become abnormal or slow.
The process of the loss of the nerve cells is a slow provess and the level of dopamine in the brain will fall over a period of time 80% of the nerve cells in the substantia nigra have gone then the symptoms begin to appear and gradually begin to worsen
The diagram above shows exactly where the substantia nigra is found in the brain.
Tourettes syndrome
Although the cause of TS is unknown, current research points to abnormalities in certain brain regions (including the basal ganglia, frontal lobes, and cortex), the circuits that interconnect these regions, and the neurotransmitters (dopamine, serotonin, and norepinephrine) responsible for communication among nerve cells. Given the often complex presentation of TS, the cause of the disorder is likely to be equally complex.
Symptoms
Tics are classified as either simple or complex. Simple motor tics are sudden, brief, repetitive movements that involve a limited number of muscle groups. Some of the more common simple tics include eye blinking and other vision irregularities, facial grimacing, shoulder shrugging, and head or shoulder jerking. Simple vocalizations might include repetitive throat-clearing, sniffing, or grunting sounds. Other complex motor tics may actually appear purposeful, including sniffing or touching objects, hopping, jumping, bending, or twisting. Simple vocal tics may include throat-clearing, sniffing/snorting, grunting, or barking. More complex vocal tics include words or phrases. Perhaps the most dramatic and disabling tics include motor movements that result in self-harm such as punching oneself in the face or vocal tics including coprolalia (uttering swear words) or echolalia (repeating the words or phrases of others). Some tics are preceded by an urge or sensation in the affected muscle group, commonly called a premonitory urge. Some with TS will describe a need to complete a tic in a certain way or a certain number of times in order to relieve the urge or decrease the sensation.
Tics are often worse with excitement or anxiety and better during calm, focused activities. Certain physical experiences can trigger or worsen tics, for example tight collars may trigger neck tics, or hearing another person sniff or throat-clear may trigger similar sounds. Tics do not go away during sleep but are often significantly diminished.
