Clinical and electrophysiological aspects of distal ulnar neuropathy

OBJECTIVES: To evaluate the use of fixed distance side to side comparison of abductor digiti minimi (ADM) and first dorsal interosseous (FDI) compound muscle action potential (CMAP) studies in the diagnosis of distal ulnar neuropathy. MATERIALS AND METHODS: Thirty normal controls underwent ADM and FDI CMAP studies bilaterally at a fixed ADM recording to stimulating point distance of 6 cm. Side to side mean latency differences to both muscles were calculated. Twenty patients with suspected unilateral distal ulnar neuropathy from routine nerve conduction studies had positive results when compared with controls. RESULTS: The upper limit of normal for side to side mean latency difference at 3 SD above the mean was 0.394 and 0.474 ms for ADM and FDI, respectively. All 20 patients had side to side mean CMAP latency difference above 3 SDs in the ADM, FDI or both muscles. Fifty percent of cases had involvement of the superficial sensory branch. CONCLUSIONS: Fixed distance side to side CMAP latency comparison is a useful electrodiagnostic adjunct for distal ulnar neuropathy. Trauma was the most common aetiology in the 20 reported cases. Correlation was found between aetiological factors and sites of lesions as localized with this method.     

Multifocal motor neuropathy: correlation of nerve ultrasound,electrophysiological, and clinical findings

We present nerve ultrasound findings in multifocal motor neuropathy (MMN) and examine their correlation with electrophysiology and functional disability. Eighty healthy controls and 12 MMN patients underwent clinical, sonographic, and electrophysiological evaluation a mean of 3.5 years (standard deviation [SD] ± 2.1) after disease onset. Nerve ultrasound revealed significantly higher cross‐sectional area (CSA) values of the median (forearm, p < 0.001), ulnar (p < 0.001), and tibial nerve (ankle, p < 0.001) when compared with controls. Electroneurography documented signs of significantly lower values of the motor conduction velocity and compound muscle action potentials (cMAPs) in the upper arm nerves (median, ulnar, radial, p < 0.001). A significant correlation between sonographic and electrophysiological findings in the MMN group was found only between cMAP and CSA of the median nerve at the upper arm (r = 0.851, p < 0.001). Neither nerve sonography nor electrophysiology correlated with functional disability. MMN seems to show inhomogeneous CSA enlargement in various peripheral nerves, with weak correlation to electrophysiological findings. Neither nerve sonography nor electrophysiology correlated with functional disability. Multicentre, prospective studies are required to prove the applicability and diagnostic values of these findings.     

Electrophysiologic features of ulnar neuropathy in childhood and adolescence

Objective

To analyze patterns of nerve injury in pediatric ulnar neuropathy (PUN).

Failure to generate baseline muscle motor evoked potentials during spine surgery: Risk factors and association with the postoperative outcomes

Objective

To identify factors associated with the failure to generate baseline muscle motor evoked potentials (mMEPs) during spinal surgery, and to determine the association between baseline mMEP generation and postoperative outcomes.

Quantitative studies of lower motor neuron degeneration in amyotrophic lateral sclerosis: Evidence for exponential decay of motor unit numbers and greatest rate of loss at the site of onset

Objective

To use our Bayesian method of motor unit number estimation (MUNE) to evaluate lower motor neuron degeneration in ALS.

Methods

In subjects with ALS we performed serial MUNE studies. We examined the repeatability of the test and then determined whether the loss of MUs was fitted by an exponential or Weibull distribution.

Results

The decline in motor unit (MU) numbers was well-fitted by an exponential decay curve. We calculated the half life of MUs in the abductor digiti minimi (ADM), abductor pollicis brevis (APB) and/or extensor digitorum brevis (EDB) muscles. The mean half life of the MUs of ADM muscle was greater than those of the APB or EDB muscles. The half-life of MUs was less in the ADM muscle of subjects with upper limb than in those with lower limb onset.

Conclusions

The rate of loss of lower motor neurons in ALS is exponential, the motor units of the APB decay more quickly than those of the ADM muscle and the rate of loss of motor units is greater at the site of onset of disease.

Significance

This shows that the Bayesian MUNE method is useful in following the course and exploring the clinical features of ALS.     

Electrical impedance myography for discriminating traumatic peripheral nerve injury in the upper extremity

Objective

To evaluate the potential of electrical impedance myography (EIM), which is sensitive to the changes in muscle structure and physiology, in discriminating traumatic peripheral nerve injury (TPNI) in the upper extremity. To identify factors that primarily influence muscle atrophy secondary to nerve injury.

Motor Unit Number Index (MUNIX) detects motor neuron loss in pre-symptomatic muscles in Amyotrophic Lateral Sclerosis

Objective

Motor Unit Number Index (MUNIX) is a quantitative neurophysiological measure that provides an index of the number of lower motor neurons supplying a muscle. It reflects the loss of motor neurons in patients with Amyotrophic Lateral Sclerosis (ALS). However, it is unclear whether MUNIX also detects motor unit loss in strong, non-wasted muscles.

Short- and long-latency afferent inhibition; uses,mechanisms and influencing factors

Transcranial magnetic stimulation (TMS) is an ideal technique for non-invasively stimulating the brain and assessing intracortical processes. By delivering electrical stimuli to a peripheral nerve prior to a TMS pulse directed to the motor cortex, the excitability and integrity of the sensorimotor system can be probed at short and long time intervals (short latency afferent inhibition, long latency afferent inhibition). The goal of this review is to detail the experimental factors that influence the magnitude and timing of afferent inhibition in the upper limb and these include the intensity of nerve and TMS delivery, and the nerve composition. Second, the neural mechanisms of SAI are discussed highlighting the lack of existing knowledge pertaining to LAI. Third, the usage of SAI and LAI as a tool to probe cognition and sensorimotor function is explored with suggestions for future avenues of research.     

Motor Unit Number Index (MUNIX) of hand muscles is a disease biomarker for adult spinal muscular atrophy

ObjectiveThere is still insufficient knowledge about natural history in adult spinal muscular atrophy, thus valid markers for treatment and disease monitoring are urgently needed.MethodsWe studied hand muscle innervation pattern of 38 adult genetically confirmed 5q spinal muscular atrophy (SMA) patients by the motor unit number index (MUNIX) method. Data were compared to healthy controls and amyotrophic lateral sclerosis (ALS) patients and systematically correlated to typical disease-relevant scores and other clinical as well as demographic characteristics.ResultsDenervation of hand muscles in adult SMA was not evenly distributed. By calculation of the MUNIX ratios, we identified a specific hand muscle wasting pattern for SMA which is different to the split hand in ALS. Furthermore, MUNIX parameters strongly correlated with established disease course parameters independent of disease stages.ConclusionWe found a pathophysiological remarkable denervation pattern of hand muscles, a ‘reversed split hand’. MUNIX of single hand muscles correlated well with disease severity and thus represents an easily available biomarker for adult SMA.SignificanceOur data show the power of the MUNIX method as a biomarker for upcoming questions in adult SMA.