A modified multiple point stimulation method for motor unit number estimation of the hypothenar muscles.

INTRODUCTION: The goal of this study is to test the hypothesis that single motor unit action potentials (SMUPs) originating from other ulnar nerve-innervated intrinsic hand muscles can inflate the motor unit number estimation (MUNE) of the hypothenar muscles. METHODS: Using the multiple point stimulation method, SMUPs recorded over the hypothenar muscles from distant origins were characterized through multichannel recordings. The MUNE calculated using only the hypothenar SMUPs was compared with estimations based on the whole ensemble. RESULTS: Of the 41 studies performed, distant SMUPs represented 17 ± 9.5% (mean ± SD) of the overall sample. MUNE calculated using only hypothenar SMUPs was 423 ± 204, compared with 537 ± 290 if all SMUPs were included (P < 0.05). The extent of increase in MUNE was highly correlated with the proportion of distant SMUPs found (r = 0.89, P < 0.05). DISCUSSION: Erroneous inclusion of SMUPs from distant muscles can significantly distort the MUNE results. Muscle Nerve 59:337-341, 2019.

Reliability of sonographic muscle thickness measurements of the thenar and hypothenar muscles.

Introduction This study was undertaken to assess the intra- and interrater reliability of sonographic thickness measurements of the thenar and hypothenar muscles. METHODS: The thickness of the thenar and hypothenar muscles of both hands of 15 volunteers (7 male, 8 female) were evaluated with a 4-13-MHz linear probe by 2 examiners who were blinded to each other's measurements. Interrater reliability was then evaluated. To assess intrarater reliability, the first examiner also performed a second measurement after an interval of at least 1 day. RESULTS: Mean age of the subjects was 31.1 ± 9.0 years. Test-retest reliability showed excellent intrarater reliability (intraclass correlation coefficient range: 0.889-0.963) and substantial to excellent results for interrater reliability (intraclass correlation coefficient range: 0.692-0.937). DISCUSSION: We found that ultrasound is a reliable method for thickness measurements of the thenar and hypothenar muscles. Muscle Nerve 57: E14-E17, 2018.

Cortical excitability differences in hand muscles follow a split-hand pattern in healthy controls.

INTRODUCTION: Differences in cortical and axonal excitability may underlie preferential atrophy of abductor pollicis brevis (APB) and first dorsal interosseous (FDI) in amyotrophic lateral sclerosis, termed the split-hand. Consequently, this study aimed to determine whether differences in excitability follow a split-hand pattern across the intrinsic hand muscles. METHODS: Excitability studies were undertaken using threshold tracking techniques in 26 healthy controls with responses recorded over APB, FDI, and abductor digiti minimi. RESULTS: Short interval intracortical inhibition was significantly greater from the APB and FDI. In addition, motor evoked potential amplitude was greater, while cortical silent period was longer from APB and FDI. At a peripheral level, the strength-duration time constant was greater when recorded over APB. CONCLUSIONS: This study establishes that differences in cortical excitability follow the split-hand pattern in healthy controls, a finding potentially explained by evolution of specialized activity of APB/FDI in complex hand tasks. Muscle Nerve 49: 836-844, 2014.

Aberrant accessory abductor digiti minimi manus muscle: a rare anatomical variation.

The hypothenar muscle with the greatest frequency of variations is the abductor digiti minimi manus. Except for morphological variations of this muscle, have also been reported cases of an extra wrist muscle, the accessory abductor digiti minimi manus muscle. This case report presents a rare case of an accessory abductor digiti minimi muscle characterized by an unusual origin from the tendons of the flexor digitorum superficialis. This anatomical variation was identified on a formalin - fixed male cadaver of Greek origin during routine dissection. This anatomical variation, which may result in Guyon's canal syndrome or complicate common wrist and hand surgical procedures such as the carpal tunnel release, should be known to orthopaedic surgeons and hand surgeons in particular.

Ulnar Artery Aneurysm in a 6-Month-Old: A Case Report.

BACKGROUND: Pediatric ulnar aneurysms are rare and, unlike their adult counterparts, cannot be explained by repetitive trauma to the palm. A small number of case reports describe diagnostic difficulty with these lesions and different treatments. METHODS: We present the case of a 6-month-old with an ulnar artery aneurysm of unknown cause. The diagnosis was supported with magnetic resonance imaging, and the lesion was resected. RESULTS: Because the hand remained well perfused, the ulnar artery was not reconstructed. CONCLUSIONS: Although the early result was good, the long-term outcome of this approach is unknown.

Intramuscular hemangioma of the hypothenar eminence. A case report.

Intramuscular hemangiomas are benign vascular tumors. They develop in striated muscles. Various sites have been reported in the literature but only rarely in the hand. We report on a case of an intramuscular hemangioma located within the hypothenar eminence, diagnosed by a biopsy. Treatment options are limited in the hand as embolization may lead to a risk of digital ischemia and sclerotherapy may lead to recurrence. This type of infiltrating tumor is poorly structured within the muscle, thus simple removal is not an option. Surgical excision of the entire affected muscle, in our case the abductor digiti minimi, was performed without any consequences on the hand's function and no signs of recurrence at the latest follow-up of 6months.