Akinesia is characterized by a difficulty in initiating voluntary movements in the absence of trigger stimuli. In other words, akinesics have a hard time when they try to start moving.
Abnormally low levels of dopamine are traditionally implicated in the onset of this disorder1 making it a common symptom among people with advanced Parkinson's disease.
Lack of dopaminergic input results in an overactivity of the globus pallidus, which, in turn, increases activity in the subthalamic nucleus2, resulting in problems with planning and initiation of movements. Akinesia is also occasionally reported as a symptom in schizophrenia3, although patients with these types of symptoms are harder to diagnose, and are, resultingly, underrepresented in clinical populations of schizophrenics. Interestingly, akinesics sometimes develop symptoms of obsessive-compulsive disorder4. This probably reflects a physiological root common to both pathologies.
Akinesia is usually treated in one of two ways. An akinesic can be given drugs (like l-dopa) that increase dopamine levels (although I also read that people are trying to treat the disorder with drugs that increase serotonin and norepinephrine levels 5). Or, in some cases, akinesia can be surgically treated; removal of the globus pallidus or the subthalamic nuclei both result in substantial reductions of akinesia6. If you're interested in going the other way, akinesia can actually be triggered by administration of sufficiently high doses of morphine7.
1. Johnson, Schallert, and Becker (1999). Akinesia and postural abnormality after unilateral dopamine depletion. Behav Brain Res Oct;104(1-2):189-196.
2. Crossman (2000). Functional anatomy of movement disorders. J Anat May;196( Pt 4):519-525.
3. Fleischhacker (2000). Negative symptoms in patients with schizophrenia with special reference to the primary versus secondary distinction. Encephale Oct;26 Spec No 1:12-14.
4. Miwa, Miwa, Imai, and Mizuno (2001). Obsessive-compulsive-like behavioral changes in pure akinesia. Parkinsonism Relat. Disord.. Oct;7(4):315-317.
5. Przuntek (2000). Non-dopaminergic therapy in Parkinson's disease. J Neurol Apr;247 Suppl 2:II19-24.
6. Tornqvist (2001). Neurosurgery for movement disorders. J Neurosci Nurs Apr;33(2):79-82.
7. Berg, Becker, and Reiners (1999). Reduction of dyskinesia and induction of akinesia induced by morphine in two parkinsonian patients with severe sciatica. J Neural Transm;106(7-8):725-728.