Paroxysmal Kinesigenic Dyskinesia in Infancy
Paroxysmal kinesigenic dyskinesia (PKD), a brief dyskinetic episode triggered by movement, may occur at any age. PKD may be primarily dystonic or choreic, or a combination of both forms may be present. Kinesigenic movements are brief, typically lasting seconds and rarely more than several minutes. Adult-onset PKD is usually secondary, caused by a structural lesion such as a multiple sclerosis plaque, infarct, or neoplasm. PKD beginning in the first or second decade is usually primary, that is, without an identifiable cause. These patients often have a family history of PKD or epilepsy. Both primary and secondary PKD typically respond well to low-dose anticonvulsants, particularly phenytoin and carbamazepine.
We present a clinical vignette and videotape of an unusual patient with primary PKD. We think this is the earliest recorded age of onset of primary PKD. According to the parents' report, attacks may have begun as early as 4 months of age and were documented by home videotape at 11 months of age. Other interesting features of these attacks included their response to clonazepam and brief improvement when temporarily discontinuing the medication.
Case Report
An 18-month-old girl was referred to the Columbia-Presbyterian Movement Disorder Center for evaluation of transient paroxysmal movements. Her delivery and early developmental history were normal. Family history was remarkable for her mother who experienced three generalized seizures at age 22. She was briefly treated with phenytoin and seizures did not recur.
At age 4 months, our patient was observed to have episodes of infrequent posturing of her legs. These events lasted seconds and occurred while she was lying on her side. Three weeks before her first birthday, the frequency of abnormal movements markedly increased. As demonstrated in the videotape (at age 11 months), seconds after crawling or even on turning to begin crawling, her legs would stiffen and turn with inversion and flexion of the feet. Her trunk and one arm were also often involved. Dystonic posturing typically lasted 5-10 seconds. During these episodes, she would often cry in distress, although she never had any alteration of consciousness, deviation of the eyes, or jerking movements of the extremities. Treatment with 0.1 mg clonazepam three times per day significantly reduced the frequency of these events but did not eliminate them. They no longer occurred when she moved, but could be triggered if she was irritated.
An extensive work-up performed prior to our evaluation included a head magnetic resonance image (with spectroscopy), electroencephalogram (EEG), urine amino and organic acids, cerebrospinal fluid and serum pyruvate and lactate, and direct DNA analysis for the DYT-1 mutation. All of these studies were normal, as was her neurologic examination. One attack occurred in the office when she became upset, similar in appearance to episodes demonstrated on the videotape. Clonazepam was slowly tapered in preparation for treatment with carbamazepine. However, because she experienced no attacks after withdrawal of clonazepam, we decided not to treat her. After 2 months without events, they recurred and she was successfully treated again with clonazepam.