The case described by Weetman et al 1 confirms the difficulty in managing drug induced (tardive) dyskinesia and dystonia, and suggests that posteroventral pallidotomy should be considered as a possible treatment option for this condition.

We report on a patient with similarly severe and refractory drug induced dystonia, and dyskinesia who responded to a right thalamotomy, a potentially safer surgical procedure than pallidotomy.2 3

A 66 year old right handed, retired newsagent had a long history of a bipolar affective disorder beginning at the age of 25 years. He had been treated with a combination of tricyclic antidepressant drugs, antipsychotic drugs, lithium carbonate, and electroconvulsive therapy. In 1993 his medication was changed from 25 mg thioridazine thrice daily to 2 mg trifluoperazine thrice daily (because of postural hypotension). Two months later the patient started to complain of abnormal neck movements associated with facial grimacing and neck pain. He was referred to a neurologist who diagnosed drug induced dystonia and dyskinesia of the head and neck and he was started on 5 mg benzhexol four times a day with no effect.

In 1995 neurological examination disclosed orofacial dyskinesia and torticollis to the left with hypertrophy of the right sternocleidomastoid muscle. He experienced stereotyped movements of the head and neck in a “no no“ fashion and dystonic posturing of the left arm. Progressive torticollis and twisting of the trunk were features that confined him to bed. He scored 36/40 on the abnormal involuntary movements scale (AIMS).4 There were no other abnormal signs. Normal investigation included routine full blood count, urea and electrolytes, liver function tests, serum and urinary copper, caeruloplasmin, venereal disease research laboratory test, and a Huntington’s trinucleotide repeat genetic analysis.

Protein electrophoresis showed an IgG paraproteinaemia but subsequent Bence Jones protein, skeletal survey, bone marrow aspirate, and trephine were normal. A CT of the head under general anaesthetic was normal. Sulpiride was cautiously introduced with an initial transient benefit; subsequent longer term treatment was unhelpful. Botulinus toxin injections were introduced at regular 3 monthly intervals with moderate effect. By January 1997 he was obtaining no relief of symptoms from botulinus injections or 200 mg sulpiride twice daily. Alternative therapies were tried and these included clonazepam, diazepam, nitrazepam, and tetrabenazine all at 125 mg thrice daily, co-careldopa at 25 mg thrice daily, and olanzapine at 15 mg once daily. Because of his Ig G paraproteinaemia he received 1.5 g methylprednisolone for 5 days with no symptomatic effect or objective change in his AIMS score.

In April 1997 ventral thalamotomy was performed on the right side in two stages under local anaesthesia. A Bennett spheroid guide had previously been inserted under general anaesthesia using CT guidance and a Leksell frame. Details of the lesions are shown in the table. The first lesion was relatively anterior and it reduced the torticollis, neck pain, hypertonia, and the dyskinesia of the contralateral limbs and allowed him to smile and laugh. One week later a second lesion was placed posteriomedial to the first. This abolished the residual “cogwheeling” of the left upper limb and improved his dexterity. There were no surgical complications. Postoperative MRI (figure) 8 months after the procedure confirms the position of the two lesions in the right thalamus.

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Postoperative MRI confirming the position of stereotaxic lesions in the right thalamus (black arrows).

Twelve months later the patient remains well with minimal dystonic neck movements and no evidence of abnormal posturing of the left arm and off all medication. His AIMS score is now 8/40.

Although the efficacy of thalamotomy has long been recognised in secondary dystonia6 we are not aware of any reports of its use in drug induced dystonia. The mechanism of drug induced dystonia is not yet known and extrapolating the surgical results for treatment of dystonia of other aetiologies may not be appropriate. The reported mortality from thalamotomy ranges from 0.4% to 6%.2Recent experience with pallidotomy indicates an incidence of severe clinical complications of between 2%-8%.2 Because of the proximity of the optic tract to the globus pallidus persistent visual defects are a well known risk of pallidotomy, up to 14% in one series.3 It is too early to be certain of long term efficacy but 12 months after operation the patient remains well and off all medication. We conclude that thalamotomy should also be considered in patients with medically refractory drug induced tardive dystonia and dyskinesia.