Abnormal Involuntary Movements







  • A.

    Paroxysmal kinesogenic dyskinesia (PKD) is characterized by sudden onset of abnormal hyperkinetic movements (dystonia, chorea, ballism, athetosis, or a combination of these) triggered by movement. Mutations in the PRRT2 gene are a common cause, but other gene mutations have been described. In paroxysmal non-kinesogenic dyskinesia (PNKD) movements can be triggered by caffeine or alcohol, or can occur spontaneously. Patients can be tested for the MR1 gene, although it is likely that mutations in yet undiscovered loci may account for some cases of PNKD. Epilepsy and functional movement disorders should always be in the differential diagnosis of patients thought to have PNKD.


  • B.

    There are few movement disorders that persist or happen exclusively during sleep. Bruxism is characterized by clenching or grinding of the teeth and/or by bracing or thrusting of the mandible. Propriospinal myoclonus is characterized by repetitive, stereotyped truncal jerks that may affect the hips and knees. Of note, many cases of propriospinal myoclonus are thought to be functional in nature. Periodic limb movements of sleep are stereotyped and intermittent movements of the ankle or knee joints. Rapid eye movement (REM)–sleep behavior disorder (RBD) is a parasomnia characterized by loss of REM sleep–associated atonia, which results in motor activity during dreaming and carries significant risk for future development of a synucleinopathy (Parkinson disease, Lewy body dementia, or multiple system atrophy). Hypnagogic myoclonus is a form of physiologic myoclonus that can occur in healthy individuals, just like hiccups or a startle response.


  • C.

    Movements that happen constantly throughout the daytime tend to be either twitch-like or choreiform. Twitch-like movements are likely to be myokymia, fasciculations, or myoclonus. Each of these movements has an electromyographic signature, and neurophysiologic studies can be used to distinguish them. Myokymia can occur in multiple sclerosis and Guillain-Barré syndrome, and after radiation therapy. Fasciculations can be a benign finding, but can also be caused by radiculopathies, entrapment neuropathies, or motor neuron disease. Myoclonus can be seen in a variety of scenarios, including genetic conditions such as myoclonus dystonia, medication side effects, and metabolic derangements (classically uremia or liver failure), and in many neurodegenerative diseases.


  • D.

    Chorea, athetosis, and ballism fall within a spectrum of hyperkinesias. Chorea consists of irregular, nonstereotyped, dance-like spontaneous movements. Huntington disease is the most common cause of generalized chorea in adults, whereas in childhood, Sydenham chorea is a common cause. In athetosis, the movements are slower and have a writhing or twisting motion, often involving the fingers. Ballism, on the other hand, is a severe form of chorea where there is violent flinging of the limbs, and is often limited to one side of the body. Hemiballism or hemichorea may be an acute presentation or delayed sequela of stroke.


  • E.

    Dystonia is due to sustained or intermittent muscle contractions causing abnormal, often repetitive movements, postures, or both. These abnormal movements are typically patterned and twisting, and may be tremulous. Other signs of dystonia include the presence of a sensory trick (improvement in movements caused by a tactile stimulus) and the presence of directionality (tendency of a dystonic body part to twist in a certain direction).


  • F.

    Tics are sudden, stereotyped movements that are often accompanied by an urge to perform the movement and a sense of relief once the movement is performed. Tics can be motor or vocal: the former are often simple movements of a body part (blinking, neck extension, grimacing, shoulder shrugging) whereas the latter is any action that causes a sound. Most tics are brief, but they can also be prolonged and ritualistic. These are known as a complex motor tics, and can be seen in patients with Tourette syndrome.


  • G.

    Functional (or psychogenic) movement disorders are common, disabling, and at times difficult to diagnose and treat. A careful history and examination may demonstrate features diagnostic of a functional movement disorder and eliminate the need for ancillary testing. Functional movements can resemble organic abnormal movements (tremor is the most common example), or be bizarre, unpredictable, and unclassifiable. Their phenomenology may change throughout the course of the examination, or be stereotyped. They may be episodic or nearly continuous. Distraction and suggestibility on examination, and entrainment (change in the frequency of a tremor during activation of the contralateral limb) are highly suggestive of a functional cause.


Algorithm 81.1

May 3, 2021 | Posted by in NEUROLOGY | Comments Off on Abnormal Involuntary Movements

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