Acquired peripheral neuropathy

Acquired peripheral neuropathy

The element of time is a crucial factor in the electrodiagnostic presentation of PN. The characteristic changes seen in various neuropathies evolve over time. If testing is performed very early in the course of the disease, abnormalities may not yet be present, in part, because the range of normal values for NCS parameters is broad. In addition, if the process is asymmetric, the affected nerves may not be sampled. Very late in the course of the disease, a multifocal process may appear diffuse and symmetric as the areas of focal involvement coalesce. A primarily, demyelinating process may begin to demonstrate secondary axonal involvement. In very severe neuropathies, it may become difficult to evoke any NCS responses to characterize the neuropathy. It is essential to place the electrodiagnostic findings within the context of the clinical progression to avoid drawing erroneous conclusions. Sometimes, the true nature of the neuropathy is clear only after sequential testing. The etiologic diagnoses of acquired polyneuropathy are vast. A well-crafted electrodiagnostic evaluation can categorize neuropathies into more specific diagnostic groups by identifying the descriptive diagnosis, significantly narrowing the list of possible etiologic diagnoses. Electrodiagnostic testing, which always starts with a pertinent history and physical examination, should always be viewed as a continuation and quantification of the physical examination. Only by knowing the extent and pattern of the clinical involvement is it possible to formulate a thorough electrodiagnostic evaluation. This knowledge is especially important in cases in which the presentation is multifocal, because the neuropathy can be missed entirely if the affected nerves are not evaluated. When evaluating a neuropathy, there are three important questions to answer: (1) Is the process diffuse or multifocal? (2) Is it demyelinating or axonal? (3) Does it predominantly involve the motor or sensory nerves? By assessing the neuropathy along these three axes, the large number of possible etiologic diagnoses becomes much more manageable.

The clinical identification of peripheral neuropathy among older persons

OBJECTIVE

To identify simple clinical rules for the detection of a diffuse peripheral neuropathy among older outpatients.

DESIGN

Observational, blinded, controlled study.

SETTING

A tertiary-care electrodiagnostic laboratory and biomechanics laboratory.

PARTICIPANTS

One hundred research subjects, 68 with electrodiagnostic evidence of peripheral neuropathy, between the ages of 50 and 80 years.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASUREMENTS

One examiner, unaware of the results of electrodiagnostic testing, evaluated Achilles' and patellar reflexes, Romberg testing, semiquantified vibration, and position sense at the toe and ankle in all subjects, and unipedal stance time and the Michigan Diabetes Neuropathy Score in a subset of subjects.

RESULTS

Significant group differences were present in all clinical measures tested. Three signs, Achilles' reflex (absent despite facilitation), vibration (128Hz tuning fork perceived for <10s), and position sense (<8/10 1-cm trials) at the toe, were the best predictors of peripheral neuropathy on both univariate and logistic regression (pseudo R(2)=.744) analyses. The presence of 2 or 3 signs versus 0 or 1 sign identified peripheral neuropathy with sensitivity, specificity, and positive and negative predictive values of 94.1%, 84.4%, 92.8%, and 87.1%, respectively. Values were similar among subgroups of subjects with and without diabetes mellitus. When other clinicians applied the technique to 12 more subjects, excellent interrater reliability regarding the presence of peripheral neuropathy (kappa=.833) and good to excellent interrater reliability for each sign (kappa range,.667-1.00) were shown.

CONCLUSION

Among older persons, the presence of 2 or 3 of the 3 clinical signs strongly suggested electrodiagnostic evidence of a peripheral neuropathy, regardless of etiology. Age-related decline in peripheral nerve function need not be a barrier to the clinical recognition of a diffuse peripheral neuropathy among older persons.

Peripheral Neuropathy Due to Cobalamin Deficiency

Vitamin B12, or cobalamin (Cbl), deficiency can produce a number of neurologic complications, including myelopathy, peripheral neuropathy, optic neuropathy, and dementia. The myelopathy, combined systems disease, is probably the most well known manifestation, and is usually readily recognized. The frequency with which peripheral neuropathy is the sole presenting feature of Cbl deficiency is a point of controversy. The prevalence and the clinical and electrophysiologic features of Cbl deficiency peripheral neuropathy have not been well characterized. In addition, there is evidence that the commonly used assays of serum Cbl are not adequately sensitive. Testing the serum metabolites methylmalonic acid and homocysteine can increase the identification of Cbl deficient patients. Treatment with parenteral Cbl injections may not produce improvement of neurologic deficits, but might prevent worsening. In some patients with Cbl deficiency, oral Cbl may be an effective therapy.

Diagnostic work-up in peripheral neuropathy: an analysis of 171 cases

This study was set up to evaluate retrospectively the efficacy of a standard diagnostic procedure, including non-invasive and invasive (spinal tap, nerve/muscle biopsy) investigations, in the diagnosis of peripheral neuropathy. The medical records of 171 in-patients with the final diagnosis of peripheral neuropathy of determined or undetermined cause were reviewed and each individual diagnostic work-up was analysed. Basic investigations included the patient's history, a clinical examination and basic laboratory tests. Depending on the individual presentation, course, and severity, further non-invasive and invasive examinations were added according to the department's standard diagnostic procedure. The aetiology could be clarified in 124 patients (73%) and remained unclear in 47 cases. Excluding cases with acute and chronic inflammatory polyneuropathy (n=14), the number of idiopathic peripheral neuropathies dropped to 33. Non-invasive investigations were sufficient to reveal the underlying aetiology in 114 cases (83 %). It is concluded that, with the application of a standard procedure for the diagnosis of peripheral neuropathy, the aetiology can be clarified in 81% of patients. In the other 19% of patients the aetiology remains idiopathic. In the majority of cases, non-invasive investigations were sufficient for diagnosis.