PubMed Health⌕ Search

Biomedical subjects

David C Preston

Publications and source records attributed to David C Preston.

15 recordsLinked to original sources
PubMed2006

Optimal recording electrode placement in the lumbrical-interossei comparison study.

The lumbrical-interossei comparison study is commonly employed in the electrodiagnosis of carpal tunnel syndrome. Placement of the recording electrodes relies on anatomic landmarks as the muscles being recorded cannot be seen or palpated. To determine the optimal active electrode location, 15 controls and 5 patients were studied using a grid of 12 electrodes placed over the lateral palm. Amplitudes, rise-times, and latencies of the responses at each location were measured. The lowest control latency difference was located in the lateral mid-proximal palm (mean 0 ms, upper range of 0.5 ms). This location also had the highest lumbrical amplitude and rise-time. More distal in the palm, the mean latency difference increased to 0.5 ms with an upper range of 0.9 ms. When performing the lumbrical-interossei comparison study, it is essential to place the active recording electrode in the optimal location. Failure to do so will result in an increased number of false-positive studies.

Adult↗
PubMed2005

Involvement of superficial peroneal sensory nerve in common peroneal neuropathy.

Motor involvement in common peroneal neuropathy (CPN) frequently shows a selective pattern with regard to deep and superficial divisions of the peroneal nerve, by clinical examination and needle electromyography. The involvement of the sensory branch of the superficial peroneal nerve (SPN) has not been well established using nerve conduction studies. Among 42 cases of electrophysiologically defined CPN in 35 patients, 37 (88%) had clinical or electrophysiologic evidence for SPN involvement, but only 20 had diminished superficial peroneal sensory response (SPSR) amplitudes. Many of the cases involving normal SPSRs had significant axonal loss involving deep peroneal motor fibers. Sparing of the superficial peroneal sensory fibers provides further evidence for the selective vulnerability of different nerve fascicles to injury. This is an important pattern to recognize; from a practical standpoint, focal segmental conduction abnormalities in the motor nerve and EMG findings can help to differentiate these lesions from L-5 radiculopathy.

Adult↗
PubMed2005

New criteria for early electrodiagnosis of acute inflammatory demyelinating polyneuropathy.

A variety of electrodiagnostic methods are used to confirm the diagnosis of acute inflammatory demyelinating polyneuropathy (AIDP), but difficulties are frequent during the first few weeks of weakness. We compared the nerve conduction studies (NCS) of patients with AIDP to those with critical illness polyneuropathy (CIP), a subacute axonal polyneuropathy. New electrodiagnostic criteria with graded certainty (normal, nondiagnostic, suggestive, highly suggestive, and definite) were designed and applied in a blinded manner to both groups. Among the AIDP patients, 64% met the highly suggestive and definite criteria (specificity 95-100%, P < 0.01), whereas 80% of the CIP group fell in the nondiagnostic criteria (P < 0.001). The relative preservation of the sural sensory response in spite of at least two abnormal sensory NCS in the upper limb suggested acute demyelination (sensitivity 48%, specificity 96%, P < 0.001) and was even more conclusive when associated with absent or prolonged F waves. Motor and sensory response amplitudes were lower in the CIP group, with comparable mean motor and sensory distal latencies and motor conduction velocities. Motor conduction blocks were present in 10% of nerves in AIDP and were not encountered in CIP. The frequency of absent or delayed F waves and absent H reflex was similar in both groups. The correlation coefficient of the cerebrospinal fluid protein concentration with the designed criteria was higher in the AIDP group (r = 0.9). We conclude that a new criterion with graded certainty is of higher specificity in the majority of patients with early AIDP.

Acute Disease↗
PubMed2005

Adult polyglucosan body disease: a case report of a manifesting heterozygote.

A 62-year-old man developed progressive gait instability, bladder dysfunction, proximal weakness, distal sensory loss, and mild cognitive impairment over 6 years. Neurologic examination revealed upper and lower motor neuron dysfunction in the lower extremities, with distal sensory loss. Electrodiagnostic studies, magnetic resonance imaging of the brain, and sural nerve biopsy were consistent with adult polyglucosan body disease. Biochemical and genetic analyses demonstrated reduced glycogen brancher enzyme levels associated with a heterozygous point mutation (Tyr329Ser or Y329S) in the glycogen brancher enzyme gene on chromosome 3. Mutational heterozygosity in the glycogen brancher enzyme gene has not been previously reported as a cause for this rare disease. A review of the clinical presentation, pathogenesis, etiology, and diagnosis of this disease is presented.

1,4-alpha-Glucan Branching Enzyme↗
PubMed2003

Iatrogenic complications and risks of nerve conduction studies and needle electromyography.

Electrodiagnostic procedures are routinely performed in patients with a variety of neuromuscular disorders. These studies are generally well tolerated and rarely thought to be associated with any significant side effects. However, needle electromyography is an invasive procedure and under certain situations has the potential to be associated with iatrogenic complications, including bleeding, infection, nerve injury, pneumothorax, and other local trauma. Similar complications are possible if needles are used for either stimulating or recording. In addition, like all other electrical devices and monitoring equipment connected to patients, electrodiagnostic testing carries the risk of stray leakage currents that under certain circumstances can result in electrical injury, especially in patients in the intensive care setting. Similarly, certain precautions are required during nerve conduction studies (NCS) in patients with pacemakers and other similar cardiac devices. In this review, we address the known and theoretical complications of NCS and needle electrode examination, and the possible methods to avoid such hazards.

Electromyography↗
PubMed2003

Entrapment and compressive neuropathies.

Entrapment and compressive neuropathies of the upper and lower extremities are frequently encountered disorders in the office. Certain clinical clues in the history and examination, along with electrodiagnostic testing and imaging studies, often suggest the correct diagnosis. Some of the more common neuropathies are discussed, along with suggestions regarding testing and treatment.

Adolescent↗
PubMed2003

Repetitive nerve stimulation and exercise testing.

Repetitive nerve stimulation and exercise testing are useful in the evaluation of patients with suspected disorders of the NMJ and muscle membrane excitability when performed with close attention to technical factors. They can be very helpful in the diagnosis of myasthenia gravis. Lambert-Eaton myasthenic syndrome, and botulism, as well as rare disorders of skeletal muscle membrane excitability, including paramyotonia congenita, myotonia congenita, myotonic dystrophy, and the periodic paralyses.

Electric Stimulation↗
PubMed2002

Electrodiagnosis of ulnar neuropathy at the wrist: conduction block versus traditional tests.

BACKGROUND: Compared to ulnar neuropathy at the elbow (UNE), ulnar neuropathy at the wrist (UNW) is rarer and more difficult to localize with routine electrophysiologic studies. METHODS: By stimulating the ulnar nerve at the wrist and palm, and recording from first dorsal interosseous (FDI), the sensitivity and specificity of conduction block (CB) and slow conduction velocity (CV) of FDI fibers across the wrist was compared to traditional electrodiagnostic techniques for localization of UNW. Twenty patients with clinically defined UNW (due mainly to wrist trauma), 30 normal controls, and 20 disease controls with severe (n = 10) and mild (n = 10) UNE were evaluated prospectively. The upper (mean +2.5 SD) and lower (mean -2.5 SD) limits for all measurements were derived from the normal controls. RESULTS: The UNW patients showed: slow wrist-palm FDI CV (<37 m/s) in 16 (80%); definite or probable CB in 14 (70%); prolonged distal latency (DL) to FDI (>4.5 milliseconds) in 12 (60%), to ulnar-innervated palmar interosseous (PI) versus median-innervated lumbrical (L) in 12 (60%), and to abductor digiti minimi (ADM) in 11 (55%). However, only CB and slow wrist-palm FDI CV (<37 m/s) were specific for UNW; prolonged DL to FDI was found in 4 patients (40%), to ADM in 4 patients (40%), and to PI in 1 patient (10%) with severe UNE. Overall, CB or slow wrist-palm FDI CV was present in 19 patients with UNW (95%). EMG failed to differentiate UNW from UNE, because forearm ulnar-innervated muscles were typically normal in UNW, but also often normal in mild UNE. CONCLUSIONS: In UNW, an additional palmar stimulation site improves electrodiagnostic yield, and demonstrates that CB is an important cause of muscle weakness.

Electric Stimulation↗
PubMed2002

Lumbrical and interossei recording in severe carpal tunnel syndrome.

Patients with severe carpal tunnel syndrome (CTS) may occasionally have absent median motor and sensory responses; in these cases, it is not possible to accurately localize the median mononeuropathy to the wrist using standard electrodiagnostic tests. We prospectively investigated the use of comparing the median motor latency to the second lumbrical and the ulnar motor latency to the interossei muscles in 28 patient hands with severe CTS and absent median motor and sensory responses. We found a prolonged latency difference in 92.8%. Along with its use in mild CTS, study of the lumbrical-interossei latency difference is helpful in patients with severe CTS with absent median motor and sensory responses.

Action Potentials↗
PubMed2002

Intrapartum maternal lumbosacral plexopathy.

There are many conflicting theories regarding the mechanism and prognosis of acute foot drop during labor. We report seven women who had arrested labor and foot drop. Six had short stature and one had a large newborn. All had weakness of ankle dorsiflexion, eversion, and inversion, and sensory loss in the L-5 dermatome. Superficial peroneal sensory nerve action potentials (SNAPs) were small or absent in six patients, and the sural SNAP was attenuated in one. Peroneal compound muscle action potential (CMAP) amplitude (recording from extensor digitorum brevis) was low in five, whereas the tibial CMAP was normal in all patients. Peroneal CMAP amplitude (recording from the tibialis anterior) was normal in three and small in three. Needle electromyography revealed decreased recruitment and fibrillation potentials in L-5-innervated muscles, mostly below the knee. We conclude that intrapartum foot drop occurs mostly in short women and is caused by lumbosacral trunk compression by the fetal head at the pelvic brim. The primary pathology is predominantly demyelination and recovery is complete in up to 5 months.

Adult↗
PubMed2002

Needle electromyography. Fundamentals, normal and abnormal patterns.

The needle electromyographic (EMG) examination is a challenging component of the electrophysiologic study. Knowledge of anatomy and physiology, sound EMG technique, and good patient rapport are required. Every muscle sampled by needle EMG is assessed for insertional activity, spontaneous activity, and voluntary motor-unit action potentials. Key pieces of information obtained from the needle EMG examination include the localization of the disorder, its chronicity, severity, and whether or not the underlying pathophysiology is neuropathic, myopathic, or associated with a neuromuscular junction disorder.

Electrodes↗
PubMed2002

Review: small-fiber neuropathy.

BACKGROUND: Most peripheral neuropathies involve large as well as small-fiber dysfunction. A small subset of neuropathies present with restricted or predominant small-fiber involvement. REVIEW SUMMARY: In this review, we discuss the differential diagnosis, clinical presentation, evaluation, and treatment of small-fiber neuropathies. Although these neuropathies are rare, their differential diagnosis is broad, and includes many disorders, including metabolic, toxic, inflammatory, infectious, and genetic etiologies. As small fibers subserve pain and autonomic functions, these neuropathies usually present with pain and temperature loss, painful dysesthesias, autonomic dysfunction, or a combination. These neuropathies are especially challenging as nerve conductions and EMG, which help guide the evaluation of most peripheral neuropathies, may have normal findings in patients with small-fiber neuropathies. Other specialized studies, including tests of autonomic function, intraepidermal nerve fiber analysis, and quantitative sensory testing, are often required to confirm the presence of a small-fiber neuropathy. In some cases, the underlying etiology can be directly treated. In most, management is limited to symptomatic treatment of sensory and autonomic dysfunction. CONCLUSION: Small-fiber neuropathies are a heterogeneous group of disorders. They vary in etiologies and require special attention, as many disorders are rare and the differential diagnosis is broad. Evaluation is often extensive and may need pathologic specimen. Many patients respond to symptomatic therapy, but some are difficult to treat.

Journal Article↗