Abnormal Gait or Movements
On observing a patient, some uncontrollable movement of the body, affecting the face, head, trunk or limbs, may be apparent.
Disordered movements may be the result of damage to the brain or nervous system, damage to the muscles, or the result of a biochemical imbalance, which may be medication related.
It should be noted that terms such as tremor, chorea, myoclonus, tics, dystonia, and athetosis are imprecise and descriptive rather than definitive. They are not confined to particular anatomical, physiological, or pathological abnormalities. Nevertheless, their use cannot be avoided and they furnish the clinician with terms that have some practical meaning.
The most prominent functions of muscle tissue are to maintain posture and produce motion. The co-ordination of muscular activity involved in maintaining posture and balance mostly takes place below the level of consciousness. By contrast, the movement of joints is mainly under voluntary control of the brain and consciously intended.
The way in which abnormal movements are categorized may be summarized as follows.
- Involuntary movement
The term involuntary movement is used in two different senses. Firstly, movements which occur below the level of consciousness are said to be involuntary movements.
Such involuntary movements are, however, entirely normal. Secondly, the execution of voluntary, willed, movements may be disrupted by unwilled and uncontrollable involuntary movements of the body, usually affecting the face, head, trunk or limbs. In this sense, all movements disorders are involuntary even when the disruption involves an interference with voluntary movement.
Akinesia (literally, without movement) denotes an absence or lack of voluntary movement while dyskinesia (literally, bad or difficult movement) is a general term used to describe difficult or distorted voluntary movement.
However, while akinesia literally means an absence or lack of voluntary movement, it has become the term of choice for the state of difficulty in initiating movements or changing from one motor pattern to another that is associated with Parkinson’s disease Opens in new window.
Information about the state of contraction and stretch of the muscle is transmitted to the brain via nerve fibres contained in each muscle. Nerve impulses transmitted in the other direction, to the muscles, stimulate them, releasing a type of neurotransmitter called acetylcholine.
This starts a chain of chemical and electrical events, involving sodium, calcium and potassium ions, which cause the muscle to contract. Potassium depletion causes muscle weakness while a decrease of calcium may cause muscle spasm.
Contracting a muscle makes it shorter and draws together the bones to which the muscle is attached. Where two or more muscles oppose each other’s actions, harmony of posture and movement requires their co-ordinated relaxation and contraction.
Apraxia is an inability to carry out a voluntary (“purposive”) movement despite normal muscle power and co-ordination. The defect is caused by damage to the nerve tracts which translate the idea of movement into actual movement.
The person knows that he wants to move in a certain way or direction but has lost the ability to recall from memory the sequence of actions necessary to achieve the desired movemement.
Ataxia (literally, without order) is an inability to co-ordinate muscles in the execution of voluntary movement. The typical ataxic gait is lurching and unsteady like that of a drunkard, with the feet widely placed and a tendency to reel to one side. This lack of co-ordination and clumsiness may affect balance and gait, limb or eye movements, and cause speech to be slurred.
Rapid, rhythmic, alternate contraction and relaxation of a group of muscles produces tremor Opens in new window. This is associated with exertion and emotional arousal, and is commonly experienced by older people, but occasionally has a greater medical significance.
- Muscle tone
Skeletal muscle is maintained in a state of partial contraction because this helps to maintain posture, keeps the eyes open, and allows the muscles to contract more efficiently. This natural muscular tension is referred to as muscle tone.
Tone therefore denotes the natural tension in the fibres of a muscle while dystonia literally means bad muscle tone. Abnormally high muscle tone causes spasticity, rigidity and resistance to movement. Abnormally low muscle tone (hypotonia) causes floppiness of the body or part of the body affected.
An individual’s muscle tone may reflect his emotional state. Strong emotion may produce a sudden loss of muscle tone, causing the individual to collapse — cataplexy. Cataplexy is commonly lasting for a number of seconds and, in three-quarters of cases, it is characteristic of narcolepsy. There is no loss of consciousness.
- Muscular rigidity
Abnormally increased muscle tone produces muscular rigidity and increased resistance to movement. Muscular rigidity is therefore the result of increased tone in one or more muscles, causing them to feel tight, with the affected part of the body becoming stiff and inflexible.
Muscular rigidity may result in unusually fixed postures, strange movement patterns, or painful muscular spasms.
- Muscular spasms
Spasms are powerful, brief, rapid, repetitive contractions of a muscle or group of muscles which are experienced as spasmodic, muscular, jerks. Hiccups, cramp, tics and habit-spasms are all types of muscular spasm.
Tics and habit-spasms may both reflect and help to release emotional tension during periods of stress and so be particularly prominent at times of psychological disturbance.
Muscles usually respond to being stretched by contracting once and then relaxing. Where stretching sets off a rapid series of muscle contractions, this is referred to as clonus (a word meaning “turmoil”). Clonus is therefore an abnormal response of a muscle to stretching and it is suggestive of damage or disease to the nerve fibres carrying impulses to that muscle. Colonic muscle contractions are a feature of seizures in grand mal epilepsy.
If clonic muscular contractions are rapid and shock-like, they may be referred to as myoclonus. Myoclonus (literally, muscular turmoil) is a sudden, brief, shock-like, uncontrollable, jerking or spasm of a muscle or muscles (“myoclonic jerks”), which may occur either at rest or during movement. hemifacial spasms (irregular shock-like contractions of the muscles on one side of the face) are a form of myoclonus.
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- Lexicon of Psychiatric and Mental Health Terms (World Health Organisation, 1989), Vol. 1, p.7.
- J. D. and J. A. Spillane, An Atlas of Clinical Neurology (Oxford Medical Publications, 1982), p.263.