Movement-related potentials and control of associated movements.

Previous studies have shown a relationship of the readiness potential (RP) preceding a motor act to motor control, as indexed by eye movement (EM). Greater EM and, therefore, less motor control was associated with increased positivity in preresponse RP components. It was hypothesized that these positive components may reflect processes involved in the inhibition of extraneous or associated movement during the performance of a motor act, especially in younger subjects with less motor development. We developed a finger lift task for detecting irrelevant associated movements (AM) from the responding hand and the nonresponding contralateral hand. During each target finger lift, small movements of the other nontarget fingers from the target hand and the contralateral hand were considered movements that should have been inhibited. Trials for each subject were divided into two bins: associated movement (AM) trials which had movement of target plus nontarget fingers, and trials with only target finger movement detected (NAM). Difference waveforms indicated a positive-going shift on trials with discrete target finger movements (NAM). Age and RP positivity at ipsilateral and posterior regions were significantly correlated. We suggest that, on trials on which associated movements are successfully inhibited, the negativity of the RP is confounded by an overlapping slow positivity. The positivity may be related to the effort needed to inhibit associated movements in order to perform a sharper and more discrete response. This relationship is a function of motor control and, indirectly, of age.

Movement-related brain potentials during hand squeezing in children and adults.

Motor readiness potentials (MRPs) during hand squeezing were recorded from scalp leads in a group of right-handed and left-handed children and adults in order to determine: (1) the relationship of the MRP to age and motor control, measured by eye movement, (2) MRP hemispheric differences during both unilateral and bilateral movements and, (3) the relationship between different MRP components. MRP components before the response were independent of those after the squeeze. MRP positivity decreased with age for all squeezes. Motor control, which increased with age, related to MRP polarity in different leads depending on the responding hand. Dominant squeezes showed the greatest MRP positivity followed by non-dominant and bilateral squeezes. Motor control followed an inverse order across tasks; as motor control increased, positivity decreased. There were no asymmetries of the MRP until squeeze onset. Asymmetry occurred only during right hand squeezes regardless of handedness.

Parathyroid adenoma and light chain myeloma.

An elderly patient with simultaneous hyperparathyroidism and light chain myeloma is described. The patient presented with hypercalcemia, bone pain, pathologic fractures, and cystic and lytic bone lesions. The problems of diagnosis and management are discussed. It is recommended that elderly patients with hypercalcemia and bone lesions should have not only diagnostic studies for hyperparathyroidism but also serum and urine immunoelectrophoresis to detect multiple myeloma or plasma cell neoplastic variants. Surgery is indicated for the hyperparathyroidism. Chemotherapy and localized radiotherapy usually control the myelomatous disease.

Follicular carcinoma of the thyroid with metastasis to the breast.

A 75-year-old woman with two previous neck operations for follicular carcinoma of the thyroid presented with a breast mass nine years after diagnosis. The mass recurred one month after excisional biopsy. Pathological examination revealed metastatic follicular carcinoma. The breast tumor was weakly positive for estrogen receptor and positive for progesterone receptor. Recurrences in the neck and breast were resected. Residual disease in the neck and metastasis to the lungs were resolved by (131)I ablative therapy. Previous reports of thyroid metastasis to the breast were described as papillary carcinoma. This report describes a rare site of metastasis and briefly reviews the pathology, diagnosis, and management of thyroid carcinoma.

Vincristine-induced dysphagia.

Dysphagia was observed in two patients receiving combination chemotherapy for metastatic carcinoma of the breast. Results of esophagogram and esophagoscopy were unremarkable. Vincristine, an anticancer drug, was incriminated as the causative agent. Cessation of vincristine therapy resulted in definite improvement. In one patient, inadvertent administration of vincristine caused prompt recurrence of dysphagia, which again disappeared upon discontinuation of the drug. The major toxicity of vincristine is neurologic. The exact mechanism for vincristine-induced dysphagia is unknown, but it does appear to be reversible.