Sensory and motor peripheral neuropathy in olivopontocerebellar atrophy

Central Nervous System Correlates of "Objective" Neuropathy in Alcohol Use Disorder

BACKGROUND

Among the neurological consequences of alcoholism is peripheral neuropathy. Relative to human immunodeficiency virus (HIV) or diabetes-related neuropathies, neuropathy associated with alcohol use disorders (AUD) is understudied. In both the diabetes and HIV literature, emerging evidence supports a central nervous system (CNS) component to peripheral neuropathy.

METHODS

In seeking a central substrate for AUD-related neuropathy, the current study was conducted in 154 individuals with AUD (43 women, age 21 to 74 years) and 99 healthy controls (41 women, age 21 to 77 years) and explored subjective symptoms (self-report) and objective signs (perception of vibration, deep tendon ankle reflex, position sense, 2-point discrimination) of neuropathy separately. In addition to regional brain volumes, risk factors for AUD-related neuropathy, including age, sex, total lifetime ethanol consumed, nutritional indices (i.e., thiamine, folate), and measures of liver integrity (i.e., γ-glutamyltransferase), were evaluated.

RESULTS

The AUD group described more subjective symptoms of neuropathy and was more frequently impaired on bilateral perception of vibration. From 5 correlates, the number of AUD-related seizures was most significantly associated with subjective symptoms of neuropathy. There were 15 correlates of impaired perception of vibration among the AUD participants: Of these, age and volume of frontal precentral cortex were the most robust predictors.

CONCLUSIONS

This study supports CNS involvement in objective signs of neuropathy in AUD.

Peripheral nerve involvement in hereditary cerebellar and multisystem degenerative disorders

Hereditary ataxias (HA) encompass an increasing number of degenerative disorders characterized by progressive cerebellar ataxia usually accompanied by extracerebellar semeiology including peripheral nerve involvement. Classically, HA were classified according to their pathological hallmark comprising three main forms: (1) spinal form predominantly with degeneration of spinocerebellar tracts, posterior columns, and pyramidal tracts (Friedreich's ataxia, FA); (2) olivopontocerebellar atrophy (OPCA); and (3) cortical cerebellar atrophy (CCA). In the 1980s Harding proposed a clinico-genetic classification based upon age of onset, modality of transmission, and clinical semeiology. The main categories in this classification were as follows: (1) early onset cerebellar ataxia (EOCA) with age of onset below 25 years and usually with autosomal recessive (AR) transmission (this group encompasses FA and syndromes different from FA); (2) autosomal dominant cerebellar ataxia (ADCA) with adult onset and with either cerebellar-plus syndrome or pure cerebellar semeiology; and (3) idiopathic late onset onset cerebellar ataxia (ILOCA). With the advent of molecular genetics, the nosology of HA has been in a state of constant flux. At present EOCA comprises at least 17 genotypes (designated with the acronym of ARCA derived from AR cerebellar ataxia), whereas under the umbrella of ADCA 30 genotypes have been reported. In this chapter we will review peripheral nerve involvement in classical pathological entities (OPCA and CCA), ARCA, ADCA, and ILOCA paying special attention to the most prevalent syndromes in each category. As a general rule, nerve involvement is relatively common in any form of ataxia except ILOCA, the most common pattern being either sensory or sensorimotor neuronopathy with a dying-back process. An exception to this rule is AR spastic ataxia of Charlevoix-Saguenay where nerve conduction studies show the characteristic pattern of intermediate neuropathy implying that sacsin mutation causes both axonal and Schwann cell dysfunction.

Multimodal neurophysiological study of SCA2 and SCA3 autosomal dominant hereditary spinocerebellar ataxias

BACKGROUND

The spinocerebellar ataxias (SCA) are a group of genetic neurodegenerative diseases, clinically and pathologically heterogeneous, characterized by slowly progressive cerebellar ataxia.

OBJECTIVE

To identify the neural pathways affected neurophysiologically, correlate the findings with the size of CAG expansion and determine the contribution of neurophysiological studies in the differential diagnosis of the two most prevalent genotypes in Spain, SCA2 and SCA3.

METHOD

We examined 10 SCA2 and 12 SCA3 patients by electromyography, electroneurography motor and sensory, multimodal evoked potentials, transcranial magnetic stimulation, blink reflex and masseter reflex. In the statistical analysis linear regression studies were performed, and the, Spearman correlation coefficient and nonparametric test U of Mann-Whitney calculated.

RESULTS

We detected the presence of a predominantly sensory neuropathy in most SCA2 patients and in a minority of SCA3 patients; the central somatosensory pathway showed significant defects in both populations. We recorded a high incidence of brain-stem electrophysiological abnormalities in SCA2 patients; in particular, the masseter reflex was abnormal in all SCA2 patients, remaining intact in all SCA3 patients. The study of cortico-spinal pathway showed a greater percentage of abnormalities in both populations than in previous studies.

CONCLUSION

SCA2 is a model of sensory neuronopathy with central and peripheral axonopathy. Studies of brain-stem pathways show a higher incidence of abnormalities in SCA2 patients. SCA3 patients show major changes in the central somatosensory pathway with relative normality of the electroneurography. The masseter reflex was the most useful test in the differential diagnosis between both genotypes.

Levodopa, methylmalonic acid, and neuropathy in idiopathic Parkinson disease

OBJECTIVE

Peripheral neuropathy (PN) is thought to be coincidental in patients with idiopathic Parkinson disease (IPD). We sought to examine the prevalence of PN in a population of IPD patients and a potential relationship to levodopa use and fasting methylmalonic acid (MMA) levels.

METHODS

In a prospective cohort study, IPD patients randomly selected from a comprehensive database were compared to control subjects regarding the presence and severity of PN using clinical and electrophysiological measures. IPD severity was determined using the Unified Parkinson's Disease Rating Scale (UPDRS). We determined the relation of levodopa use with serum levels of cobalamin, MMA, and homocysteine (Hcy). We also explored the association between presence and severity of PN and age, duration of IPD, cumulative levodopa dosing, cobalamin, MMA, and Hcy levels.

RESULTS

Fifty-eight randomly selected IPD patients were compared to 58 age- and sex-matched controls. PN was present in 55% of IPD patients and 9% of controls. Patients with IPD had greater prevalence of PN and fasting MMA/Hcy levels than controls. IPD patients with PN were older and exhibited higher UPDRS scores, fasting MMA/Hcy levels, and cumulative levodopa exposure. PN severity in IPD subjects positively correlated with both levodopa exposure and MMA levels.

INTERPRETATION

IPD patients have a higher prevalence of PN than controls. Although causality is not established, levodopa exposure is associated with MMA elevation and sensorimotor neuropathy in IPD patients. Cobalamin replacement concurrent with levodopa therapy should be considered to protect against development of PN in IPD patients.

Neuropathy as a potential complication of levodopa use in Parkinson's disease

The presence and potential etiologies of peripheral neuropathy (PN) in patients with Parkinson's Disease (PD) is unknown. We examined for presence of PN in patients with PD. From a PD patient population of 500 patients screened for features of symptomatic PN, patients were further selected for clinical, electrophysiological, and laboratory studies related to PN. This PD patient population with idiopathic PN (PD-IPN) was compared to a group of PD patients without PN (PD-only), and a large group of patients without PD with idiopathic PN (IPN) for abnormalities in Cbl, fasting homocysteine (Hcy), and fasting methylmalonic acid (MMA) levels. PD-IPN and IPN patients identified with abnormalities in Cbl, Hcy, or MMA levels were treated with intramuscular Cbl for 1 to 2 years. Of 49 PD patients with symptomatic PN, 34 patients (69%) had PD-IPN, and 32/34 (94%) had abnormal Hcy or MMA levels as compared to 26/258 (10%) of IPN patients. Cumulative lifetime L-dopa dosage and fasting MMA levels were associated with PN severity. Cbl therapy led to improvements in Hcy and MMA levels in all groups, and PN in PD-IPN patients stabilized during therapy. PN in PD patients may be associated with iatrogenic Cbl metabolic abnormalities. Alternatively PN may be a peripheral nervous system manifestation of PD.

Polyneuropathy in autosomal dominant cerebellar ataxias: phenotype-genotype correlation

Autosomal dominant cerebellar ataxias (ADCAs) are clinically and genetically heterogeneous neurodegenerative disorders. The aim of this study was to evaluate electrophysiologically peripheral nervous system involvement in each of the groups studied and its correlation with the number of CAG repeats. Forty patients with ADCA were clinically and electrophysiologically investigated. Thirty-five patients belonged to the ADCA type I group (SCA1, 12; SCA2, 10; SCA3, 13) and five to the ADCA type II group. Axonal sensory or sensorimotor polyneuropathy was found in 42% of the SCA1 patients, 80% of the SCA2 patients, and 54% of the SCA3 patients, whereas electrophysiological studies were normal in all those with ADCA type II. The number of CAG repeats was significantly higher in SCA1 patients with polyneuropathy than in those without polyneuropathy (P = 0.01), whereas the reverse was observed in SCA3/MJD (Machado-Joseph disease) patients (P = 0.05). We conclude that axonal polyneuropathy is often associated with ADCA type I, but its frequency varies according to factors such as the locus responsible and the number of CAG repeats.

Correlation of peripheral nerve fiber loss and trinucleotide repeats in Machado-Joseph disease

BACKGROUND

Machado-Joseph disease (MJD) is a dominantly inherited cerebellar ataxia associated with spasticity, ophthalmoplegia and dystonia. There has been no report of electrophysiological or histological alterations of the peripheral nervous system in patients with MJD.

METHODS

Four patients with MJD were identified by polymerase chain reaction. The peripheral nerves of these patients were subjected to electrophysiological testing and histological study. Correlation analyses were made between various clinical parameters and the electrophysiological and histological changes.

RESULTS

Electrophysiological studies demonstrated a marked reduction of sensory action potential, acute denervation changes on needle EMG, as well as mild decrease in the compound motor action potential. Light microscopy of the sural nerves revealed clear loss of myelinated fibers, and morphometry studies showed a loss of large myelinated fibers. Moreover, the severity of these pathological changes was found to be related to the CAG repeat length in the MJD gene.

CONCLUSION

Our findings indicated that the peripheral nervous system was frequently affected in patients with MJD. These findings were similar to those seen in Friedreich's ataxia, suggesting a loss of sensory and motor fibers probably following a lesion of the dorsal root ganglion and the anterior horns in the spinal cord. Furthermore, the number of CAG repeats seems to have an inverse relationship to the extent of pathological changes of the peripheral nerves.

Changes of unmyelinated nerve fibers in sural nerve in amyotrophic lateral sclerosis, Parkinson's disease and multiple system atrophy

Quantitative changes in unmyelinated nerve fibers (UMNFs) of sural nerves in patients of amyotrophic lateral sclerosis (ALS), Parkinson's disease (PD) and multiple system atrophy (MSA) were evaluated using autopsy materials whose pathological diagnosis had been confirmed by careful postmortem examinations. Ordinary ALS cases demonstrated no involvement in cutaneous UMNFs; however, the patients with long survival due to the application of ventilatory support showed bimodality in UMNF diameter histograms, and a patient with involvement of systems other than motor pathways showed an abnormal value in two indices: a low percentage of subunits containing axon(s) and a high mean number of Schwann cell profiles per axon. A significant reduction of the mean value of UMNF density (21%) was found in PD patients. Because the density of myelinated nerve fibers did not show any significant decrease as compared with age-matched controls, the change of nerve fibers in peripheral nervous system was considered to be confined to UMNFs in PD. Elderly PD cases showed enhanced changes in the ageing process, as expressed by the two indices described above. In MSA, the mean value of UMNF density was significantly decreased (23%), and this decrease almost paralleled that of myelinated nerve fiber density. Abnormal values for the two indices described above were found and two out of four cases demonstrated bimodality in the diameter histogram of UMNFs. Unlike MSA, ALS and PD have not been included in the disorders with cutaneous UMNF involvement. Our results supply the first evidence of morphological changes in cutaneous UMNFs in PD cases. In ordinary ALS cases, the emergence of such morphological changes is suggested in cases with long survival.

Axonal motor and sensory neuropathy in myotonic dystrophy

We report the neurophysiological findings from 24 subjects with myotonic dystrophy of Steinert and the histological findings in two of them. The conduction data is compared with that of a group of subjects with Landouzy-Déjérine muscular dystrophy. In 46% of cases, the electrophysiological data revealed slight and generalized axonal neuropathy. Histological results of sural nerve confirmed axonal damage of sensory fibres. The neuropathy was not correlated with age of patients, duration or onset of the disease, nor with the state of the deep reflexes; it did not show signs of progressing and is probably one of the multisystemic manifestations of gene pleiotropism.

AAEM minimonograph #34: polyneuropathy: classification by nerve conduction studies and electromyography

Electrodiagnostic evaluation of patients with suspected polyneuropathy is useful for detecting and documenting peripheral abnormalities, identifying the predominant pathophysiology, and determining the prognosis for certain disorders. The electrodiagnostic classification of polyneuropathy is associated with morphologic correlates and is based upon determining involvement of sensory and motor fibers and distinguishing between predominantly axon loss and demyelinating lesions. Accurate electrodiagnostic classification leads to a more focused and expedient identification of the etiology of polyneuropathy in clinical situations.

Neurophysiological study in chronic GM2 gangliosidosis (hexosaminidase A and B deficiency), with motor neuron disease phenotype

We report the electrophysiological investigation of two adult cases with GM 2 gangliosidosis with hexosaminidase A and B deficiency. Superficial peroneal biopsy was obtained from one patient. The electrophysiological alterations of the peripheral nervous system were fasciculations, signs of collateral reinnervation and loss of motor units, decrease in sensory potential amplitude and increase in distal motor latency. Increase in N9-N13 interpeak latency of the somatosensory evoked potentials and an increase I-V interpeak latency of the brain-stem auditory potentials were evident in both cases. Visual evoked potentials were normal. Nerve biopsy showed a severe loss of myelinated fibers, especially of those with the largest diameter, with no signs of segmental demyelination, or remyelination. A tentative interpretation of our findings is given.