Evaluation of central motor conduction in hypothyroid and hyperthyroid patients

Evaluation of visual functions in Iranian hypothyroid adults

INTRODUCTION

The aim of this study was to investigate the effects of hypothyroidism on visual functions such as visual acuity, refractive errors, colour vision, and contrast sensitivity, among hypothyroid adults.

METHODS

Forty-three patients with clinical hypothyroidism along with 43 age- and sex-matched healthy individuals underwent visual examinations, including visual acuity, refractive errors, eye deviations with the cover test, colour vision with the D15 test, and contrast sensitivity with Pelli-Robson test.

RESULTS

It was indicated that visual acuity, refractive errors, phoria, and colour vision had no significant difference between the hypothyroid and control groups. Contrast sensitivity decreased in hypothyroid subjects as compared with controls. The mean values of binocular contrast sensitivity were 1.85 ± 0.09 log in the hypothyroid group and 1.93 ± 0.09 log in controls, which showed a statistically significant difference (p = .03).

CONCLUSIONS

Our findings illustrated a reduced contrast sensitivity in adult hypothyroidism. Since CS is related to functioning and quality of life, a comprehensive and detailed eye examination may be beneficial for hypothyroidism patients.

A comprehensive review of transcranial magnetic stimulation in secondary dementia

Although primary degenerative diseases are the main cause of dementia, a non-negligible proportion of patients is affected by a secondary and potentially treatable cognitive disorder. Therefore, diagnostic tools able to early identify and monitor them and to predict the response to treatment are needed. Transcranial magnetic stimulation (TMS) is a non-invasive neurophysiological technique capable of evaluating in vivo and in “real time” the motor areas, the cortico-spinal tract, and the neurotransmission pathways in several neurological and neuropsychiatric disorders, including cognitive impairment and dementia. While consistent evidence has been accumulated for Alzheimer’s disease, other degenerative cognitive disorders, and vascular dementia, to date a comprehensive review of TMS studies available in other secondary dementias is lacking. These conditions include, among others, normal-pressure hydrocephalus, multiple sclerosis, celiac disease and other immunologically mediated diseases, as well as a number of inflammatory, infective, metabolic, toxic, nutritional, endocrine, sleep-related, and rare genetic disorders. Overall, we observed that, while in degenerative dementia neurophysiological alterations might mirror specific, and possibly primary, neuropathological changes (and hence be used as early biomarkers), this pathogenic link appears to be weaker for most secondary forms of dementia, in which neurotransmitter dysfunction is more likely related to a systemic or diffuse neural damage. In these cases, therefore, an effort toward the understanding of pathological mechanisms of cognitive impairment should be made, also by investigating the relationship between functional alterations of brain circuits and the specific mechanisms of neuronal damage triggered by the causative disease. Neurophysiologically, although no distinctive TMS pattern can be identified that might be used to predict the occurrence or progression of cognitive decline in a specific condition, some TMS-associated measures of cortical function and plasticity (such as the short-latency afferent inhibition, the short-interval intracortical inhibition, and the cortical silent period) might add useful information in most of secondary dementia, especially in combination with suggestive clinical features and other diagnostic tests. The possibility to detect dysfunctional cortical circuits, to monitor the disease course, to probe the response to treatment, and to design novel neuromodulatory interventions in secondary dementia still represents a gap in the literature that needs to be explored.

Thyroid disease and the nervous system

Thyroid disorders are common in the general population and in hospitalized patients. Thyroid disease may present first with neurological complications or else may occur concurrently in patients suffering other neurological disorders, particularly those with an autoimmune etiology. For this reason neurologists will commonly encounter patients with thyroid disease. This chapter provides an overview of the neurological complications and associations of disorders of the thyroid gland. Particular emphasis is placed on conditions such as thyrotoxic periodic paralysis and myxedema coma in which the underlying thyroid disorder may be occult leading to a first, often emergency, presentation to a neurologist. Information about clinical features, diagnosis, pathogenesis, therapy, and prognosis is provided. Emphasis is placed on those aspects most likely to be relevant to the practicing neurologist and the interested reader is directed to references to good, recent review articles for further information.

Neuromuscular findings in thyroid dysfunction: a prospective clinical and electrodiagnostic study

OBJECTIVES

To evaluate neuromuscular signs and symptoms in patients with newly diagnosed hypothyroidism and hyperthyroidism.

METHODS

A prospective cohort study was performed in adult patients with newly diagnosed thyroid dysfunction. Patients were evaluated clinically with hand held dynamometry and with electrodiagnosis. The clinical features of weakness and sensory signs and the biochemical data were evaluated during treatment.

RESULTS

In hypothyroid patients 79% had neuromuscular complaints, 38% had clinical weakness (manual muscle strength testing) in one or more muscle groups, 42% had signs of sensorimotor axonal neuropathy, and 29% had carpal tunnel syndrome. Serum creatine kinase did not correlate with weakness. After 1 year of treatment 13% of the patients still had weakness. In hyperthyroid patients 67% had neuromuscular symptoms, 62% had clinical weakness in at least one muscle group that correlated with FT4 concentrations, but not with serum CK. Nineteen per cent of the patients had sensory-motor axonal neuropathy and 0% had carpal tunnel syndrome. The neuromuscular signs developed rapidly, early in the course of the disorder and were severe, but resolved rapidly and completely during treatment (average time 3.6 months).

CONCLUSIONS

Neuromuscular symptoms and signs were present in most patients. About 40% of the hypothyroid patients and 20% of the hyperthyroid patients had predominantly sensory signs of a sensorimotor axonal neuropathy early in the course of thyroid disease. Weakness in hyperthyroidism evolved rapidly at an early stage of the disorder and resolved completely during treatment, suggesting a functional muscle disorder. Hand held dynamometry is sensitive for the detection of weakness and for the clinical evaluation of treatment effects. Weakness in hypothyroidism is more difficult to treat, suggesting myopathy.

The diagnostic value of motor evoked potentials

OBJECTIVE

To assess the diagnostic usefulness of motor evoked potentials (MEPs) and to identify the optimal method for calculating the central conduction time. The test results were evaluated in a prospective study of 1023 neurological patients.

METHODS

We evaluated the correlation between clinical and electrophysiological findings, the accuracy, the sensitivity, the percentage of subclinical abnormalities and the false negative rates of MEPs in different neurological disorders. In patients with lower motor neuron involvement, we compared the central conduction time calculated as the difference between the latency of the cortical and magnetic root stimulation responses with that calculated using the F-wave method.

RESULTS

The agreement index between electrophysiological and clinical findings was 87%. The overall accuracy of the test was 0.97. The higher sensitivity values were demonstrated in spinal cord disorders (0.85), hereditary spastic paraplegia (0.80) and motor neuron diseases (0.74). The higher percentages of subclinical abnormalities were found in motor neuron disorders (26%) muscular diseases (24%), multiple sclerosis (13.5%) and spinal cord diseases (12.5%). The higher false negative rates were found in sylvian stroke (0.36) and hereditary spastic paraplegia (0.16). Central conduction study using magnetic paravertebral stimulation but not using the F-wave method, resulted in 12% and 10% of false positive values in lower limb multiradiculopathies and in neuropathies, respectively.

CONCLUSIONS

MEPs represent a highly accurate diagnostic test. MEP clinical value is maximum in motor neuron, muscle and spinal cord diseases. In patients with lower motor neuron involvement, the gold standard for central conduction determination is the F-wave method.