ACUTE DYSTONIA

    DEFINITION

    Dystonia is a brief or sustained muscle spasm, often with slow
    abnormal movements.  Although any muscle group may be involved, it
    most commonly affects facial muscles (eyes, jaw, tongue). 

    TOXIC CAUSES

    Numerous pharmaceutical agents are associated with acute dystonic
    reactions.  Important examples include:

         Benzamides:         metoclopramide
                             sulpiride
         Butyrophenones:     haloperidol
         Chloroquine and hydroxychloroquine
         Cocaine
         Levodopa
         Lithium
         Phenothiazines, especially piperazine compounds:
                             trifluoperazine
                             perphenazine
                             fluphenazine
                             prochlorperazine 
                             thiethylperazine

    Serotonin syndrome and neuroleptic malignant syndrome are specific
    toxic syndromes, associated with increased muscle tone, that
    require specific management.

    NON-TOXIC CAUSES

    Degenerative:       Spinocerebellar degeneration

    Focal dystonias:    Blepharospasm
                        Writer's cramp

    Infective:          Encephalitis
                        Tetanus

    Metabolic:          Thyrotoxicosis
                        Wilson's disease

    Structural:         Arterio-venous malformation
                        Cerebrovascular accident
                        Tumour

    CLINICAL FEATURES

    Onset of dystonia may occur up to 20 hours following the
    administration of the causative agent.

    Various types of dystonia, involving particular muscle groups have
    been described:

         Laryngeal dystonia - spasm of pharyngeal and laryngeal muscles
         resulting in stridor.

         Oculogyric crisis - spasm of extra-ocular muscles, forcing the
         eyes into upward or lateral gaze.

         Opisthotonus - spasm of all paravertebral muscles, forcing the
         trunk and neck into hyperextension.

         Retrocollis - spasm of paravertebral neck muscles, forcing the
         neck into hyperextension.

         Torticollis - spasm of lateral neck muscles, twisting the neck
         to one side.

    DIFFERENTIAL DIAGNOSIS

    Catatonic states
    Dyskinesias 
    Seizures (tonic phase)

    RELEVANT INVESTIGATIONS

    Usually, no specific investigations are required to evaluate acute
    toxic dystonias.  Where indicated, the following may be useful:

         CPK
         EEG or CT scan of head (to exclude seizures or central organic
         lesions)
         Toxicology screens
         Urinalysis

    TREATMENT

    Dystonias may increase in severity after initial presentation and
    therefore all patients should be treated.  Initial treatment is
    usually provided with a parenteral formulation, followed by oral
    medication for 2 to 3 days to prevent recurrence.  Milder forms can
    be treated with oral medication alone.

    Suggested agents include:

     Benztropine 1 to 2 mg by intramuscular or intravenous injection 
    (0.02 mg/kg in children).  This dose may be repeated in 10 minutes
    if the response is incomplete and anticholinergic side effects have
    not occurred.  Follow with 1 mg (0.02 mg/kg in children) orally
    every 12 hours for 2 days.  Benztropine is not the agent of choice
    in children less than 3 years of age.

     Diphenhydramine 1 mg/kg intravenously or intramuscularly to a
    maximum of 30 mg. This dose may be repeated in 30 minutes if the
    response is incomplete and anticholinergic side effects have not
    occurred.  Follow with 25 mg (0.5 mg/kg in children) orally, every
    6 hours for 2 days.

     Diazepam 0.1 mg/kg by slow intravenous injection.  This dose may
    by repeated in 30 minutes if the response is incomplete and
    excessive sedation has not occurred.

     Procyclidine  5 to 10 mg (0.5 to 2 mg in children under 2 years
    of age, 2 to 5 mg in children over 2 years of age) intramuscularly
    or intravenously.  This dose may be repeated after 20 minutes if
    the response is incomplete.  Follow with 2.5 mg orally every 8
    hours for 2 days.

    CLINICAL COURSE AND MONITORING

    Patients should be observed until symptom free.  Prior to
    discharge, they should be instructed that recurrent dystonia can
    occur for up to 48 hours.  In this event, they should return for
    medical evaluation.  The clinical course may be prolonged in the
    case of dystonic reactions following injection of depot
    preparations.

    LONG-TERM COMPLICATIONS

    Unusual.

    AUTHOR(S)/PEER REVIEW

    Author:   Robert Dowsett
              Consultant Toxicologist
              Departments of Clinical Pharmacology and Emergency
              Medicine
              Westmead Hospital
              Westmead, NSW 2145
              Australia

    Peer Review:   London, March 1998: P. Dargan, T. Della Puppa, L.
                   Murray, A. Nantel, M. Nicholls.