Case study: Asphyxia caused by inspissated oral and nasopharyngeal secretions.

An institutionalized man with severe mental disability and cerebral palsy, admitted from the ED with suspected aspiration pneumonia, died after a long struggle with respiratory difficulties. The cause of death was determined to be asphyxia resulting from a complete obstruction of the posterior pharynx and upper larynx by thickened oral and nasopharyngeal secretions. Although airway obstruction is common in people with motor or neurologic disorders and in those who are chronically debilitated or institutionalized, food and foreign matter are not the only culprits. This case serves to remind clinicians that a failure to provide good oral care and adequate hydration is not only poor practice but can result in death.

Ulnar nerve motor conduction to the first dorsal interosseous muscle.

The ulnar motor study to the abductor digiti minimi (ADM) is commonly performed, but does not test the terminal deep palmar branch of the ulnar nerve. Although damage to the ulnar nerve most often occurs at the elbow, the damage may occur elsewhere along the course of the nerve, including damage to the deep palmar branch. Ulnar conduction studies of the deep branch have been performed with recording from the first dorsal interosseous (FDI) muscle. These studies have used differing methodologies and were mostly limited by small sample size. The aim of this study was to develop a normative database for ulnar nerve conduction to the FDI. A new method of recording from the FDI was developed for this study. It utilizes recording with the active electrode over the dorsal first web space, with the reference electrode placed at the fifth metacarpophalangeal joint. This technique reliably yields negative takeoff measurements. An additional comparison was made between ulnar motor latency with recording at the ADM and with recording at the FDI. For this study, 199 subjects with no risk factors for neuropathy were tested. The latency, amplitude, area, and duration were recorded. The upper limit of normal (ULN) was defined as the 97th percentile of observed values. The lower limit of normal (LLN) was defined as the 3rd percentile of observed values. For the FDI, mean latency was 3.8 +/- 0.5 ms, with a ULN of 4.7 ms for males, 4.4 ms for females, and 4.6 ms for all subjects. Mean amplitude was 15.8 +/- 4.9 mV, with a LLN of 5.1 for all subjects. Side-to-side differences in latency to the FDI, from dominant to nondominant hands, was -0.1 +/- 0.4 ms, with a ULN of 0.8 ms. For the amplitude, up to a 52% decrease from side to side was normal. For the same-limb comparison of the FDI and ADM, the mean latency difference was 0.6 +/- 0.4 ms, with a ULN increase of 1.3 ms for latency to the ADM versus the FDI.

An antidromic study of the medial antebrachial cutaneous nerve, with a comparison of the differences between medial and lateral antebrachial cutaneous nerve latencies.

Electrodiagnostic study of the medial antebrachial cutaneous (MAC) and lateral antebrachial cutaneous (LAC) nerves is not routinely undertaken. Pathology of either nerve or of the brachial plexus may occur from a variety of causes. Iatrogenic injury of these nerves has been rarely reported, but potential exists for nerve damage with a number of medical procedures, implants, or surgeries in the flexor forearm. In any of these situations, nerve conduction studies on the MAC and the LAC can be of benefit. Previous studies have reported normal values and examined side- to-side differences in the LAC, but have not compared the latencies of the MAC to the LAC in the same limb. This study establishes normal nerve conduction study values for the MAC from 207 subjects with no risk factors for neuropathy, using a 10-cm distance and an antidromic technique. It also examines both side-to-side differences in the MAC and same-limb differences between the MAC and LAC. For this study, the upper limit of normal (ULN) was defined as the 97th percentile of observed values. The lower limit of normal (LLN) was defined as the 3rd percentile of observed values. The onset latency, peak latency, onset-to-peak amplitude, peak-to-peak amplitude, rise time, and duration were recorded. For the MAC, the mean onset latency was 1.7 +/- 0.2 ms, with a ULN of 2.0 ms. Mean peak latency was 2.2 +/- 0.2 ms, with a ULN of 2.6 ms. Onset-to-peak amplitude was 13 +/- 7 muV, with a LLN of 4 muV. Peak-to-peak amplitude was 10 +/- 7 muV, with a LLN of 3 muV. Side-to-side differences in MAC onset and peak latencies were 0.0 +/- 0.2 ms, with a ULN of 0.3 ms. Up to a 67% side-to-side decrease in MAC onset-to-peak amplitude was within the normal range. A 78% side- to-side decrease in MAC peak-to-peak amplitude was within the normal range. For the same-limb comparison of the MAC and the LAC, both onset and peak latencies had a mean difference of 0.0 +/- 0.2 ms and a ULN of 0.3 ms, regardless of whether the MAC or the LAC had the longer latency.

Acceptable differences in sensory and motor latencies between the median and ulnar nerves.

The median and ulnar nerves are often studied during the same electrodiagnostic examination. The sensory and motor latencies of these nerves have been compared to detect a common electrodiagnostic entity: median neuropathy at the wrist. However, this comparison could also be used to diagnose less common ulnar pathology. For this reason, it is important to establish normal values for comparing median and ulnar sensory and motor latencies. Previous research deriving these differences in latency has had some limitations. The purpose of this study was to derive an improved normative database for the acceptable differences in latency between the median and ulnar sensory and motor nerves of the same limb. Median and ulnar sensory and motor latencies were obtained from 219 and 238 asymptomatic risk-factor-free subjects, respectively. An analysis of variance was performed to determine whether physical characteristics, specifically age, race, gender, height, or body mass index (as an indicator of obesity), correlated with differences in latency. Differences in sensory latencies were unaffected by physical characteristics. The upper limit of normal difference between median and ulnar (median longer than ulnar) onset latency was 0.5 ms (97th percentile), whereas the peak latency value was 0.4 ms (97th percentile). The upper limit of normal difference between ulnar-versus-median (ulnar longer than median) onset latency was 0.3 ms (97th percentile), whereas the peak-latency value was 0.5 ms (97th percentile). The mean difference in motor latencies correlated with age, with older subjects having a greater variability. In subjects aged 50 and over, the mean difference in median-versus-ulnar latency was 0.9 ms +/- 0.4 ms. The upper limit of normal difference (median longer than ulnar) was 1.7 ms (97th percentile). The upper limit of normal ulnar motor latency is attained if the ulnar latency comes within 0.3 ms of the median latency. In individuals less than 50 years of age, the mean difference in latency was 0.6 ms +/- 0.4 ms, with the median latency usually being greater than the ulnar. The upper limit of normal difference (median longer than ulnar) was 1.4 ms (97th percentile), whereas the upper limit of ulnar latency relative to median latency was attained if the ulnar latency was equal to median latency.

An introduction to electromyography: an invited review.

Electromyography is a complex diagnostic test that is useful in diagnosing many neuromuscular and musculoskeletal conditions. Physiatrists and neurologists become familiar with this test during their training, while other physicians have minimal or no exposure, outside of perhaps some basic physiology lectures. A review of the anatomy, physiology, and physics upon which electrodiagnostic testing is based and of the various techniques used during a study provides the necessary foundation for understanding and using study results. A discussion of the conditions for which electrodiagnostic testing is useful, including carpal tunnel syndrome, radiculopathy, peripheral neuropathy, and disorders of the neuromuscular junction, is included both to review these disorders and to encourage appropriate referral for electrodiagnostic study.