Neurology India Medknow Publications on behalf of the Neurological Society of India ISSN: 0028-3886 EISSN: 1998-4022 Vol. 52, Num. 2, 2004, pp. 276-278

Neurology India, Vol. 52, No. 2, April-June, 2004, pp. 276-278

Letter To Editor

Cervical dystonia responsive to levodopa

Singh Sumit , Goyal Vinay , Prasad Kameshwar , Behari Madhuri

Department of Neurology, Neuroscience's Centre, All India Institute of Medical Sciences, New Delhi-110029

Correspondence Address:Department of Neurology, Neuroscience's Centre, All India Institute of Medical Sciences, New Delhi-110029

Code Number: ni04094

Sir,
Spasmodic torticollis (ST) or idiopathic cervical dystonia (ICD), the most common adult segmental dystonia,[1] is characterized by recurrent or sustained abnormal head postures. Drugs like trihexiphenydyl, clozapine,[2] and mexiletine[3] have been tried for treatment with an unfavorable response or with intolerable side-effects. Local botulinum toxin injections are currently the treatment of choice for ST.[4] We report a case with cervical dystonia showing favorable response to levodopa.

A 23-year-old male started having intermittent turning of his neck to the right for two years, when he was 21 years old. It was observed at rest and disappeared while doing farm work in the field. Over the next month he had to abandon his work as his condition aggravated and his head remained turned to the right for most of the day. There were no other abnormal movements, or diurnal variation in his symptom. The symptom improved during sleep. He did not report any geste antagonistic. He was prescribed propanolol and trihexiphenydyl without appreciable benefit. Levodopa with carbidopa (100+25-mg), one tablet twice daily improved his torticollis completely, but the effects continued only for two to three hours after the administration. He visited our center after discontinuing the drugs. He was born of a non-consanguineous marriage and there was no family history of dystonia, significant psychological stress, or trauma to the neck or head. The past medical history was not significant.

The torticollis made his head turn to the right by 70-80 degrees. The rotation persisted for 75% of the waking time of the day. Even forceful straightening of his neck was unsuccessful. There was no head tilt or shoulder elevation. His speech and cranial nerves including the ocular fundii were normal. Keyser Fleischer ring was absent on slit lamp examination. There was no muscle wasting or muscle weakness and muscle tone was normal in all the muscles except the left sternocleidomastoideus. The deep tendon reflexes were normal bilaterally, with a flexor plantar response. There were no tremors on his extremities and no other involuntary movements were discernible apart from the torticollis.

The routine hemogram, serum biochemistry, serum copper and ceruloplasmin levels were normal. MRIs of the brain and the cervical spine were normal. Diagnosis of idiopathic cervical dystonia was made and he was put on 6mg/day of trihexiphenydyl, without any favorable response. A further increase in the doses was associated with intolerable side-effects. A therapeutic trial with levodopa was considered based on his past history and 300 mg of levodopa with decarboxylase inhibitor per day was started in three divided doses. In one week the twist of his neck decreased by more than 75% and he could easily maintain a straight position of his neck. Levodopa was stopped to confirm that the clinical improvement was indeed due to the drug. In 24 hours his symptoms recurred to the pre-treatment level. Controlled release levodopa (levodopa 200 mg + Carbidopa 50 mg) was started to sustain the clinical response for a longer period of time. The patient became symptom-free and was discharged on 600 mg per day of levodopa (controlled release). He has been symptom-free until now.

It appears that our patient was an atypical case of dopa-responsive dystonia, however, it is difficult to exclude the possibility of a particular type of ICD responding to levodopa, based on clinical evaluation. Younger age of onset, absence of geste antagonistic and responsiveness to levodopa were features against the diagnosis of ICD. In the presence of normal serum biochemistry and normal neuroimaging studies it is unlikely that the patient had secondary dystonia. Small, open-label trials of levodopa[5] and dopamine agonists. in patients with ST have been without success.

Dopa-responsive dystonia (DRD) occurs typically in childhood, starts in the lower limbs and exhibits marked diurnal variation, and patients eventually develop parkinsonian features. These patients respond to low doses of levodopa. Involvement of the neck muscles is very rare in patients with DRD and has only been reported as minimal retrocollis.[6] There were reports of DRD that showed torticollis associated with generalized dystonia, but there has been no report of DRD starting with torticollis or showing torticollis as a predominant feature.

Onset at an ′older′ age, absence of diurnal variation and features of parkinsonism were against the diagnosis of DRD in this case. DRD is characterized by an age-dependent occurrence of symptoms and diurnal variation of symptoms might be absent in about 25% patients,[7] particularly in patients with onset in the older age. Our patient could be a representative of such a group of patients of DRD. On close evaluation it appears that ′dystonia′ and ′dopa responsiveness′ are the key features of DRD, both of which were present in our case.

CSF neopterin assay, oral phenylalanine loading test,[8] cultured lymphocytic GTP cyclohydrolase (GCH1) activity and direct GCH1 gene sequence analysis can help in the diagnosis of DRD, but none of these tests is confirmatory. The GCH1 gene (located on the chromosome 14q 22.1-q 22.2).is the candidate gene for DRD.[9] Genetic analyses can confirm the diagnosis of DRD in 60% of cases and up to 40% of cases can be sporadic. The availability of these tests could confirm the diagnosis in our case, however, as none of the above mentioned tests are confirmatory, our patient could still have DRD with an atypical presentation. While typical cases of DRD rarely elude diagnosis, in atypical cases of dystonia a significant response to levodopa could be a pointer to the disease. We conclude that in atypical cases of dystonia, a therapeutic trial of levodopa could be attempted. The need for diagnostic tests, which can help in the confirmation of the clinical diagnosis in a reliable and reproducible manner in such atypical cases, cannot be therefore, overemphasized.

References

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