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Movement disorders are conditions involving abnormal involuntary movements of a part of the body. These can occur due to several causes, and are uncommonly associated with stroke. A tremor may develop for the first time following a stroke, either immediately after it, or in a subacute manner.
The tremor is usually caused by strokes due to small vessel disease of the brain, in the areas supplied by the middle or posterior cerebral arteries which include the basal ganglia. These structures are responsible for relaying and regulating voluntary muscle contraction, and impaired function can thus lead to tremor and other movement disorders.
Hemorrhagic strokes are more typically responsible for the onset of tremor and other movement disorders than ischemic strokes. The location and type of stroke may thus be suggested by the acute onset of a tremor. Multifocal or segmental vascular interruption is mostly associated with this type of condition.
Most tremors occurring as sequelae of cerebrovascular accidents are action tremors, but may contain postural and resting components as well.
A tremor can be caused by either a stroke or the abnormal blood vessels responsible for many strokes. Strokes in the pons or midbrain are often linked to acute head tremors.
On the one hand, a resting tremor in Parkinsonism can resolve the tremor, while acute-onset Parkinsonism may be the first indication of a stroke involving the substantia nigra. Rubral, thalamic, and brainstem strokes are all known to produce specific syndromes which include tremor, including Benedikit syndrome, and Claude syndrome, both of which cause tremors on the side opposite to that affected.
Other movement disorders may also occur as stroke sequelae, with hemiballism or hemichorea being among the most common.
A characteristic type of tremor called Holmes’ tremor is also called rubral tremor, midbrain tremor, or cerebellar outflow tremor. It is a resting tremor seen in one of the limbs, which is exaggerated by the initiation of movement. It becomes more intense with intentional or directional action. It is a low-frequency tremor of less than 4.5 Hz, and irregular, usually involving an upper limb.
Its importance in this context is that it is often associated with stroke involving the brainstem, and sometimes the cerebellum or thalamus. It is a result of impaired or altered conduction along one or other of the primary pathways involving the basal ganglia and the thalamic nuclei. The dentate, rubral, or inferior olivary nuclei are often involved. Holmes’ tremor usually occurs weeks to months after a stroke.
This is another type of tremor which occasionally follows a stroke. In this type of tremor, there are rapid involuntary contractions of the soft palate which were previously mistaken for palatal myoclonus. The movements are rhythmic, and they persist during sleep, though at a different rate.
Patients with symptomatic palatal tremor show other signs which indicate cerebellar involvement, impaired brainstem reflexes, and poor motor learning.
The pathology involves the red nucleus, the inferior olivary nucleus, and the dentate nucleus, all of which are involved in a feedback loop between the cerebellar nuclei and the brainstem that controls the motor impulses from the spinal cord. Loss of this feedback leads to impaired rhythmic discharge within the loop, leading to the onset of the palatal tremor.
A Parkinsonian resting tremor may also have an acute onset after a stroke in the basal ganglia or midbrain, especially when it is the initial sign of a stroke in the medial tract of the substantia nigra.
Diffuse small vessel disease in the brain can produce vascular Parkinsonism, which is associated in some cases with a mild resting tremor. This may be improved to a small extent for a short duration by the administration of levodopa or other dopaminergic drugs.
On the other hand, the action tremor of pseudoparkinsonism is a sign of diffuse cerebral damage, when associated with other signs such as apraxia and paratonic rigidity.
Tremor following stroke is an uncommon manifestation, and is usually self-limited, with over 90 percent of cases resolving within 6 months. In studies, approximately 28 percent of patients with tremor have shown complete disappearance of the tremor, while 64% have shown partial resolution.
Response to drugs is variable, with good efficacy being observed in some cases and a poor response in others.
Surgical treatment consists of deep brain stimulation in the thalamic region, and selective thalamotomy in the area of the nucleus ventralis intermedius.
Other measures include occupational and physical therapy, including weighing down the affected limb to reduce the amplitude of tremor. Functional neurosurgery is resorted to if the tremor is severe.