Biomedical subjects

Michael Rezak

Publications and source records attributed to Michael Rezak.

6 recordsLinked to original sources

PubMed2006

Two cases of ischemia associated with subthalamic nucleus stimulator implantation for advanced Parkinson's disease.

Deep brain stimulation is generally a safe and effective method of alleviating motor impairment in advanced-stage Parkinson's disease patients. However, adverse events of surgery have been noted, such as hemorrhage, infection, seizures, and device failure. In this report, we describe 2 cases of the unusual adverse event of ischemia associated with subthalamic nucleus stimulator implantation. We present the intraoperative neurological symptoms, microelectrode recording data, imaging findings, and other correlated events. In the first case, the clinical effects of ischemia were evident intraoperatively and coincided with silence during microelectrode recording from the ischemic region. In the second case, the timing of the ischemic event could not be determined precisely but also was associated with a difficult mapping. Subcortical ischemia may be an underrecognized event that confounds neurophysiological mapping of deep brain structures and affects clinical outcomes.

Aged↗

PubMed2005

Visual system side effects caused by parasympathetic dysfunction after botulinum toxin type B injections.

Botulinum toxin type B (BTX-B) has been approved by the Food and Drug Administration for the treatment of cervical dystonia. However, as with botulinum toxin type A (BTX-A) it has off-label uses, such as for hyperhidrosis, focal dystonias, spasticity, and facial wrinkles. BTX-B has also been shown to be a safe and effective alternative for patients who are resistant to BTX-A. The most commonly reported side effects include dry mouth and dysphagia. To date, there have been few reports of visual disturbances associated with BTX-B use. In this study, we report on three individual patients who received BTX-B and who subsequently developed parasympathetic dysfunction of the visual system after injections of BTX-B at remote sites.

Adult↗

PubMed2003

Qualitative analysis of verbal fluency before and after unilateral pallidotomy.

This study examined qualitative aspects of phonemic and semantic fluency before and after unilateral pallidotomy in patients with intractable Parkinson's Disease (PD). Specifically, clustering (number of similar words generated sequentially) and switching (number of changes or switches from one cluster to another) were evaluated for both fluency tasks. Twenty-five PD patients participated and were grouped according to whether they improved or declined on each of the fluency measures after surgery. Decliners evidenced decreased switching, but not clustering, suggesting difficulties with set-shifting and cognitive flexibility rather than a diminished semantic store of information or retrieval difficulties. Though consistent with hypotheses about difficulties with executive processing after pallidotomy, a series of correlational analyses with composite measures of neuropsychological functioning (attention, language, executive processing, and memory) suggest caution in interpreting these findings. In these analyses, clustering was not meaningfully related to any of the composites whereas switching was significantly and positively related to the composites; this pattern emerged, for the most part, on both fluency measures before and after surgery. Switching, but not clustering, was also significantly and positively correlated with total words generated on both semantic and phonemic fluency. Switching changes across time were also related to DRS changes post-pallidotomy. These correlational analyses challenge the specificity of the switching variable and, more broadly, the validity of these qualitative measures of verbal fluency.

Aged↗

PubMed2003

Facial nerve neuritis secondary to ultraviolet radiation.

We describe a patient who developed facial nerve injury following significant exposure to UV radiation. A 49-y-old construction worker developed erythema and edema on the left side of his face (exposed side) 12 h after working within 18 in of a compromised metal halide incandescent light bulb for a total of 2 h. One month later, the patient noted a painful burning sensation over the left side of his face associated with marked left facial weakness and inability to close his eye (peripheral VIIth nerve palsy). Two months later, synkinetic left facial movements were consistent with aberrant regeneration. Over the next several months, forceful episodic spasmodic activity developed in the muscles of facial expression on the left, identical to that seen in hemifacial spasm. Rarely has UV radiation been implicated in damage to subcutaneous nerves. This case demonstrates that significant neurologic morbidity may follow high exposure to UV radiation.

Diagnosis, Differential↗

PubMed2002

Motor and cognitive sequelae of unilateral pallidotomy in intractable Parkinson's Disease: electronic measurement of motor steadiness is a useful outcome measure.

This study examined the short-term motor and cognitive sequelae of unilateral posterolateral pallidotomy for patients with intractable Parkinson's Disease (PD). Unique to this study was the inclusion of electronic motor steadiness instrumentation among pre- and postsurgical assessment procedures. Fifteen PD patients underwent right-sided surgery and 10 underwent left-sided surgery; patients were evaluated 1 month presurgery and approximately 3 months postsurgery. Motorically, there were no significant changes in grooved pegboard or maze-drawing performances, but patients evidenced significantly improved steadiness, particularly in the hand contralateral to the side of surgery. Cognitively, there were no significant decrements on postsurgery composite variables comprised of well-known tests of attention, executive functioning, delayed memory or recognition memory; these findings were similar for patients with either left- or right-sided surgery. There was, however, a significant change in language abilities among a subset of patients. This change was evident in the decline in verbal fluency in PD patients who underwent left-sided pallidotomy, a finding that has consistently emerged in pallidotomy outcome studies. This decline is discussed in terms of evidence that suggests that the basal ganglia consist of several separate, but parallel circuits, some of which are important for cognition.

Aged↗

PubMedDate not supplied

Acute chorea associated with metoclopramide use.

Metoclopramide is a dopamine receptor antagonist that is used to treat diabetic gastroparesis, chemotherapy-induced nausea, and migraines. It is known to cause extrapyramidal side effects such as tardive dyskinesia, parkinsonism, dystonia, and akithisia, but not chorea. We describe a patient who presented with choreiform movements shortly after the administration of intravenous metoclopramide. Her work-up for secondary causes of chorea was otherwise negative and her symptoms abated with the administration of oral quetiapine and intravenous diazepam.

Acute Disease↗