Paroxysmal Hemidyskinesia Related to a Large Thalamic Cyst

Introduction

Symptomatic thalamic lesions are more frequently related to stroke, usually causing contralateral sensory symptoms, and less often to contralateral movement disorders. Thalamic lesions leading to movement disorders have been reported in cases of multiple sclerosis, perinatal injury, AIDS, thyroid and parathyroid abnormalities, basal ganglia calcification, cystinuria, encephalitis, meningioma, and Leigh syndrome. These causes of dyskinesias are relatively rare, and only a few isolated cases have been described and reviewed during the last 3 decades.[1,2]

Sporadic paroxysmal dyskinesia (PDK) may be an even less frequent clinical presentation of structural lesions of the thalamus. In a classic series of 62 patients with thalamic and subthalamic lesions, only 3 presented clinically with PDK with contralateral dystonia: Two were related to stroke and 1 was related to multiple sclerosis.[1] The attacks were precipitated by voluntary movements in all patients. All cases had discrete focal lesions in the posterolateral or ventrolateral thalamus, with involvement of the internal capsule.[1]

We report a case of an adolescent who developed PDK with a mixed presentation of paroxysmal nonkinesigenic dyskinesia (PNKD) and paroxysmal hypnogenic dyskinesia (PHD) restricted to the hand and foot, particularly in the fingers and toes, with an unusually high number of attacks per day and night. Radiologic investigation showed a large thalamic cyst, contralateral to the hemidyskinesia. To the best of our knowledge, there are no similar cases in the literature.

Case Presentation

A 15-year-old, unmarried woman was referred to our neurology department because of intermittent, abnormal, involuntary movements of the right hand and foot, and especially in the fingers. These movements had started 2 months before the consultation and were becoming more frequent, with longer duration of attacks. Initially, the attacks lasted 1 minute or less, and they typically happened once or twice a day. At the time of the consultation, the duration of the attacks lasted from a few seconds to up to 30 minutes, and were occurring dozens of times a day, affecting very restricted areas of her body. The patient also mentioned that, by the time of the consultation, she was awakened by 4–5 attacks every night. She had not identified any triggering factors at any time during these 2 months, and she noted no premonitory symptoms preceding the attacks. When the attacks lasted longer than a couple of minutes, the hand or foot would take on a dystonic posture and she experienced cramplike pain in the affected area.

Of interest, the fifth finger and the fifth toe were always the most affected. The attack could involve either the hand or the foot alone, or it could involve both, but the episodes never progressed from these areas (Videos 1–3). She experienced no mirror effect on the left side of her body either in resting conditions or during movements. Although the patient did not describe this symptom, examiners noted a mild degree of right hemihypoesthesia to the touch during the neurologic examination. Strength was preserved in all 4 limbs.

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Video 1. Video shows episodic dyskinesia of right fingers and toes.

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Video 2. Dyskinesia of toes of right foot.

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Video 3. Dystonic cramping of right foot.

Clinical History

The patient had undergone open heart surgery at the age of 9 to correct partial anomalous drainage from the pulmonary vein into the right atrium, via the left innominate vein. At the time of the diagnosis, her only symptom involved feeling tired when she played more vigorous games or went cycling. Although she was diagnosed at the age of 6, the surgeon delayed surgery until she reached the age of 9, when an increased flow into the coronary sinus was detected. The patient experienced no complication relating to this corrective surgery, and the cardiologist released her from further investigations when she was 11 years old, 4 years before she noted the present symptoms. During our investigation, she was evaluated by a cardiologist who did not find any heart problems.

Clinical Course

The electroencephalogram showed no abnormalities during the attacks. Carbamazepine had been administered by another service, but was discontinued when it failed to improve her symptoms.

Considering the possibility that this dystonia could be responsive to dopamine, we administered low doses of levodopa. The patient's symptoms worsened significantly within 24 hours of receiving the medication, and it was withdrawn. While waiting for the results from MRI of her brain, we began prednisone, 1 mg/kg/day, on the basis of a possible diagnosis of multiple sclerosis.

At this time, the attacks were so frequent that the patient was unable to attend school, and the pain in her fingers and toes was almost continuous. With prednisone, the attacks decreased in frequency and duration to 2–3 attacks per day, lasting less than 5 minutes. Night attacks no longer occurred. Prednisone was continued for 4 weeks, with progressive tapering of the daily dose. Two months after the suspension of prednisone, she continues to experience occasional attacks.

MRI showed a large thalamic cyst (1.2 × 0.8 × 1.0 cm) of benign appearance, which did not communicate to the ventricular system and caused no mass effect (Figure). No perilesional edema and no cyst wall abnormalities could be detected. Although this lesion might be a lacuna or a lacuna-like cyst, because the patient is doing well, we decided not to investigate it further with surgical procedures. With the short course of prednisone, her symptoms have stabilized, and now she experiences brief attacks only very rarely.

Figure.

Left thalamic cyst of possible neuroepithelial origin.

Discussion

The thalamus relays input from the peripheral sensory pathways, basal ganglia, and cerebellum to the premotor cerebral cortex. The medial globus pallidus projects its output to the ventrolateral thalamus via the lenticular fasciculus, whereas other connections enter Forel's fields to form the thalamic fasciculus in the subthalamic region. The subnucleus of the globus pallidum also receives afferent excitatory projections from the subthalamic nucleus, via the subthalamopallidal projections, through the subthalamic fasciculus. Therefore, the thalamus plays a very important role in controlling movement, particularly when there is pallidal inhibition.[3]

Lesions in the thalamus that lead to movement disorders are mainly of vascular origin; few other causes have been reported.[1] Typically, such lesions have been seen in association with paroxysmal attacks of dyskinesia initiated by voluntary, repetitive movements. In the case reported here, we found a cystic lesion of the thalamus that appeared to be related to a form of dyskinesia that was not triggered by repetitive movements. Such attacks could also occur during sleep, thus characterizing PNKD in association with PHD.[2]

To the best of our knowledge, no cases of thalamic cysts leading to PNKD and PHD have been reported. This case may be a fortuitous association of congenital heart disease and thalamic cyst, or these 2 conditions may be linked in that they could both be congenital malformations. The radiographic appearance of the thalamic cyst suggested that it was neuroepithelial, which could indeed mean that it is of congenital origin.

Neuroepithelial cysts in the thalamus are rare and usually small. They are often an incidental and asymptomatic finding.[4] There is a report of 2 cases of neuroepithelial cysts of the basal ganglia that were associated with complex movement disorders and required stereotactic drainage.[5]

Although speculation is difficult, our patient may have experienced sudden growth in an otherwise asymptomatic cyst, and this may have caused the dyskinesia to appear. The idea that the treatment with corticosteroids interfered in such growth can only be taken as an untestable hypothesis. Because the patient is nearly asymptomatic, there is no indication for a surgical intervention at this time.