Extensor Indicis Proprius Muscle Research Articles

Different Muscles, Lower Cutoff Values: Does it Truly Improve the Diagnostic Sensitivity of Repetitive Nerve Stimulation in Myasthenia Gravis?

ABSTRACT Context: This study evaluated the diagnostic accuracy of repetitive nerve stimulation (RNS) compared with single-fiber electromyography (SF-EMG) in generalized myasthenia gravis (MG). Aims: The aim of the study was to determine the diagnostic sensitivity of RNS in various muscles and assess the effect of varying decrement cutoff values on diagnostic efficacy. Setting and Design: This was a prospective study of 34 confirmed generalized MG patients. Subjects and Methods: RNS was performed on five muscles. Clinical features, autoantibody presence, and SF-EMG jitter rates recorded from the frontalis muscle were analyzed. Patients were classified according to the MG Foundation of America classification. Statistical Analysis: SPSS version 23 was used for descriptive statistics, comparisons of categorical and quantitative data, and correlation analysis, with the significance level set at P < 0.05. Results: Among the patients (58.8% males and mean age = 59.47 ± 13.37 years), SF-EMG detected increased jitter in 91.2%, whereas RNS identified a significant decrease of 50% across at least one muscle. The decremental response was >10% in the abductor digiti minimi (ADM), trapezius, nasalis, abductor pollicis brevis, and extensor indicis proprius muscles in 5.9%, 26.5%, 29.4%, 11.8%, and 29.4% of patients, respectively. A sensitivity improvement at lower decrement values was observed only in the ADM muscle. A significant correlation was found between decreases in the trapezius muscle and seropositivity. Conclusions: Optimal muscle selection improves RNS diagnostic accuracy in MGs. The study recommends incorporating the spinal accessory and radial nerves in RNS due to their high sensitivity, although modifying the decrement cutoff value has a limited overall effect.

Variations in the extensor indicis proprius muscle in the Burmese population: implications for hand reconstructive surgery

BackgroundThe use of extensor indicis proprius (EIP) muscle tendon for tendon grafting and transplantation in the management of hand injuries is common. Anatomical variations of the EIP tendons have been reported with variable prevalence and presentation in different populations worldwide. Knowledge of possible variation patterns is crucial in reconstructive surgery. The current study aims to describe the prevalence of anatomical variations of the EIP in the Burmese population. MethodsA total of 50 cadavers (39 males, and 11 females) were dissected. Both upper limbs of each cadaver were observed. The presence of the EIP, the number of tendons, the origin and insertion of the muscle and its relation with the extensor digitorum communis (EDC) were recorded and variations reported. ResultsOf the 100 limbs studied in the 50 cadavers, only 1/100 limb was reported to have an absent EIP muscle and tendon. Of the remaining 99/100 limbs examined, one of them consists of a double tendon, that is, EIP and extensor indicis et medii communis (EIMC) were inserted separately onto the index finger and middle finger respectively on the dorsum of the left hand. Further to this, there is one case in which an extra muscle belly was observed in the EIP tendon, this muscle is commonly known as the extensor digitorum brevis manus muscle. All the EIP variations were observed in the male cadavers only. ConclusionOf the 50 cadavers studied, 3/100 limbs exhibited EIP variations in the current studied population. Population-specific studies on these variations may aid in a better understanding of the different anatomical patterns of the muscles in the dorsum of the hand. This may lead to improved diagnosis and surgical management of injuries to the dorsum of the hand and for the use of the EIP tendon in surgical grafts and transplantations.

Reconstruction of Hand Dorsum Defect Using Double Perforators-Based Anterior Interosseous Artery Island Flap: A Case Report and Description of a New Anterior Interosseous Artery Perforator.

The anterior interosseous artery (AIA) perforator flap is not commonly used in hand dorsum reconstruction compared with alternatives. However, it is a versatile flap with several advantages. Literature on the AIA perforator flap is based on the dorsal septocutaneous branch (DSB), which branches from the AIA and passes through fascia between the extensor pollicis longus (EPL) and extensor pollicis brevis muscles. In the described case, the authors reconstructed a hand dorsum defect in a 78-year-old man using an AIA perforator flap with double perforators supplied by the DSB and a new perforator branching from the distal than DSB. No complication was encountered, and the flap survived completely. A retrospective computed tomography review revealed the presence of the new perforator in 14 of 21 patients. Two types of new perforator were observed. One passed through the ulnar side of the extensor indicis proprius (EIP) muscle and penetrated fascia between the extensor digitorum minimi and extensor digitorum communis tendons, whereas the other passed between the EPL and EIP muscles. This report describes the anatomical location and clinical application of the new AIA perforators. The double perforators-based AIA flap provides a straightforward, reliable means of reconstructing hand dorsum defects.

Sympathetic skin responses and electromyographic reaction times in chronic autoimmune thyroiditis: An overlooked electrodiagnostic study.

Objectives This study aims to evaluate peripheral nerve functions, sympathetic skin responses (SSRs), and electromyographic (EMG) reaction times in hypothyroid patients and to compare them to healthy individuals. Patients and methods Between January 2007 and September 2007, a total of 54 patients with Hashimoto’s thyroiditis including 35 euthyroid (3 males, 32 females; mean age: 45.2±10.2 years; range, 35 to 60 years) and 19 with subclinical hypothyroidism (2 males, 17 females; mean age: 43.2±12.6 years; range, 40 to 65 years) were included in the study. The control group consisted of 35 healthy individuals (5 males, 30 females; mean age: 39.1±9.3 years; range, 29 to 52 years). Nerve conduction studies (NCSs), SSRs of the hand and foot obtained by stimulation of the contralateral median nerve, and EMG reaction times of the extensor indicis proprius muscle were performed in all subjects. Results There was no significant difference in peripheral NCSs and SSRs between patients and the control group. However, reaction times were longer in the AIT patients compared to the healthy individuals suggesting alterations in cognitive function related to the primary disease process in AIT. Conclusion Electrodiagnosis of autonomic nervous system involvement and cognitive impairment can be challenging in AIT. However, EMG reaction times and SSRs are practical and useful tools that are often overlooked. On the other hand, SSRs may be combined with more quantitative tests, such as sudomotor axon reflex testing, to allow us to better determine the extent of involvement of the autonomic nervous system in AIT.

Importance of Anatomic Peculiarities and Ultrasound-Guided Electromyography of the Extensor Indicis Proprius Muscle.

The extensor indicis proprius muscle (EIPM) is considered a key muscle in the assessment of the level of the neurologic lesion causing any motor or sensory medio-cubital impairment of the hand.The aim of this study is to illustrate the anatomical peculiarities of the EIPM, the ultrasound (US) anatomy of the inferoposterior part of the forearm, and the technique of US-guided electromyography (EMG) of the EIPM.The US-guided EMG of the EIPM is technically easy and safe for young practitioners, provided there is a good knowledge of US anatomy of the inferoposterior part of the forearm.

Morphology of Extensor Indicis Proprius Muscle in the North Indian Region: An Anatomic Study with Ontogenic and Phylogenetic Perspective

Morphology of Extensor Indicis Proprius Muscle in the North Indian Region: An Anatomic Study with Ontogenic and Phylogenetic Perspective

Extensor indicis proprius muscle and its variants together with the extensor digitorum brevis manus muscle: a common classification. Clinical significance in hand and reconstructive surgery.

The extensor indicis proprius (EIP) is a muscle of the forearm that originates from the posterior surface of the ulna and the adjacent interosseous membrane and attaches to the index finger. Many anatomical variations of this muscle have been reported in the literature. The extensor digitorum brevis manus (EDBM) is a variant muscle found on the back of the wrist and hand. These muscle variants should be considered in the context of clinical syndromes and reconstructive hand surgery. The aim of the present study was to describe in detail the normal and variant anatomy of these muscles and propose new systematic classifications. Formol-carbol-fixed Europid upper limbs (n = 176) were examined in the Department of Anatomy, Histology and Embryology at the Medical University of Sofia for variations of the EIP and occurrences of the EDBM. We found normal anatomy in 147 (84%) of the specimens examined and we measured the length and width of the muscle belly and tendon of the EIP. Variations of the EIP in the other 29 upper limbs (16%) included replacement of the EIP by an EIB, coexistence of the EIP and EIB, presence of accessory tendons, and additional muscles. Knowledge of anatomical variations of forearm muscles is important because they can cause clinical syndromes or have implications for reconstructive surgery, most often as tendon transfers in response to functional loss of other forearm muscles.

Extensor indicis proprius tendon transfer using shear wave elastography

The means for judging optimal tension during tendon transfers are approximate and not very quantifiable. The purpose of this study was to demonstrate the feasibility of quantitatively assessing muscular mechanical properties intraoperatively using ultrasound elastography (shear wave elastography [SWE]) during extensor indicis proprius (EIP) transfer. We report two cases of EIP transfer for post-traumatic rupture of the extensor pollicis longus muscle. Ultrasound acquisitions measured the elasticity modulus of the EIP muscle at different stages: rest, active extension, active extension against resistance, EIP section, distal passive traction of the tendon, after tendon transfer at rest and then during active extension. A preliminary analysis was conducted of the distribution of values for this modulus at the various transfer steps. Different shear wave velocity and elasticity modulus values were observed at the various transfer steps. The tension applied during the transfer seemed close to the resting tension if a traditional protocol were followed. The elasticity modulus varied by a factor of 37 between the active extension against resistance step (565.1 kPa) and after the tendon section (15.3 kPa). The elasticity modulus values were distributed in the same way for each patient. The therapeutic benefit of SWE elastography was studied for the first time in tendon transfers. Quantitative data on the elasticity modulus during this test may make it an effective means of improving intraoperative adjustments.

Neuromorphic meets neuromechanics, part II: the role of fusimotor drive

Objective. We studied the fundamentals of muscle afferentation by building a Neuro–mechano–morphic system actuating a cadaveric finger. This system is a faithful implementation of the stretch reflex circuitry. It allowed the systematic exploration of the effects of different fusimotor drives to the muscle spindle on the closed-loop stretch reflex response. Approach. As in Part I of this work, sensory neurons conveyed proprioceptive information from muscle spindles (with static and dynamic fusimotor drive) to populations of α-motor neurons (with recruitment and rate coding properties). The motor commands were transformed into tendon forces by a Hill-type muscle model (with activation-contraction dynamics) via brushless DC motors. Two independent afferented muscles emulated the forces of flexor digitorum profundus and the extensor indicis proprius muscles, forming an antagonist pair at the metacarpophalangeal joint of a cadaveric index finger. We measured the physical response to repetitions of bi-directional ramp-and-hold rotational perturbations for 81 combinations of static and dynamic fusimotor drives, across four ramp velocities, and three levels of constant cortical drive to the α-motor neuron pool. Main results. We found that this system produced responses compatible with the physiological literature. Fusimotor and cortical drives had nonlinear effects on the reflex forces. In particular, only cortical drive affected the sensitivity of reflex forces to static fusimotor drive. In contrast, both static fusimotor and cortical drives reduced the sensitivity to dynamic fusimotor drive. Interestingly, realistic signal-dependent motor noise emerged naturally in our system without having been explicitly modeled. Significance. We demonstrate that these fundamental features of spinal afferentation sufficed to produce muscle function. As such, our Neuro–mechano–morphic system is a viable platform to study the spinal mechanisms for healthy muscle function—and its pathologies such as dystonia and spasticity. In addition, it is a working prototype of a robust biomorphic controller for compliant robotic limbs and exoskeletons.

Optimal Radial Motor Nerve Conduction Study Using Ultrasound in Healthy Adults.

ObjectiveTo obtain reference values, to suggest optimal recording and stimulation site for radial motor nerve conduction study (RmNCS), and to analyze the correlation among RmNCS parameters, demographics and ultrasonography (US) findings.MethodsA total of 55 volunteers participated in this study. We hypothesized that ‘lateral edge of spiral groove (A)’ was the optimal stimulation site, and the ‘largest cross-sectional area (CSA) of extensor indicis proprius (EIP) muscle (B)’ was the optimal recording site. The surface distance between ‘A’ and the lateral epicondyle of the humerus divided by upper arm length, was named the spiral groove ratio. The surface distance between ‘B’ and the ulnar styloid process divided by forearm length, was named the EIP ratio. Using US, we identified these sites, and further conducted RmNCS.ResultsData was collected from 100 arms of the 55 volunteers. Mean amplitude and latency were 5.7±1.1 mV and 5.7±0.5 ms, respectively, at the spiral groove, and velocity between elbow and spiral groove was 73.7±7.0 m/s. RmNCS parameters correlated significantly with height, weight, arm length, and CSA of the EIP muscle. Spiral groove ratio and EIP ratio were 0.338±0.03 and 0.201±0.03, respectively; both values were almost the same, regardless of age, sex and handedness.ConclusionWe established a reference value and standardized method of RmNCS using US. Optimal RmNCS can be conducted by placing the recording electrode 20% (about one-fifth) of forearm length from the ulnar styloid process, and stimulating at 34% (about one-third) of the humeral length from the lateral epicondyle.

Emergency repair of extensor tendon central slip defects with Oberlin's bypass technique: Feasibility and results in 4 cases with more than 5 years of follow-up

Treatment of soft tissues defects in the central slip of the extensor tendon at the proximal interphalangeal (PIP) joint is challenging because of the potential for stiffness and boutonniere deformity. The bypass procedure proposed by Oberlin for secondary injuries is an attractive solution. This salvage procedure uses a free tendon graft (palmaris longus) that is intercalated between the extensor indicis proprius muscle and the base of the middle phalanx. This study reports on the first cases of acute central slip defect treated in an emergency setting. Four patients with an average age of 37years (range 11–69) were treated by the same surgeon using the bypass procedure. Clinical evaluations consisted of measuring the active range of motion in the PIP joint, QuickDASH, Total Active Motion (TAM) and strength with a Jamar® dynamometer. All patients had reintegrated their injured finger into their body image within three months. At the last follow-up, the average active mobility was 0–5–76.5°. The functional outcomes were similar at nine months, with an average mobility of 0–13–72°. The two patients who were working at the time of injury were able to return to work in the third month. Various procedures such as tendon plasty, transfer or graft have been described in the literature for posttraumatic chronic boutonnière deformity. In cases where significant defects exist not only in the tendon, but the bone and skin, the bypass procedure is an effective approach to achieving satisfactory functional outcomes.

An Anomalous Accessory Extensor Indicis Proprius Muscle: A Case Report

Variations related to tendon insertion and musculotendinous junction of the extensor proprius indicis muscle are commonly encountered. An anomalous extensor indicis proprius muscle (EIP) tendon was detected in a fifty-year-old female cadaver during routine dissection of the right upper extremity. The body of tendon was initiated from the posterior ulna as a one muscle body, then continued as two separate muscle bodies and tendons and finally they were separated into two slips after passing the fourth dorsal compartment. As a radial part, it was divided into two slips at the level of the first metacarpophalangeal joint, and conjugated with the extensor pollicis longus (EPL) muscle. Then, as an ulnar part, it was terminated at the radial side of the lateral band of the second metacarpophalangeal joint. Familiarity with the normal anatomy and variations of the tendons may help to prevent confusion and mistakes during tendon repairs, and tendon transfers.

Anomalous Extensor Indicis Proprius Muscle

Anomalous Extensor Indicis Proprius Muscle

Motor somatotopy of extensor indicis proprius and extensor pollicis longus

After tendon transfer of extensor indicis proprius (EIP) to extensor pollicis longus (EPL), rehabilitation is initiated to enhance motor cortex reorganization. However, patients have been described showing thumb extension immediately after the tendon transfer. At cortical level, no evidence supports either of these assumptions. We noninvasively investigated motor cortical source locations of EIP and EPL muscles. Magnetoencephalography was used to identify motor somatotopic map in healthy right-handed participants, who performed voluntary extension at index metacarpophalangeal joint and thumb interphalangeal joint. Motor cortical representation of EIP was more medial than cortical representation of EPL, with mean Euclidean distance of 15.4±2.7 mm. Motor somatotopic map of EIP/EPL that was obtained by magnetoencephalography supports 'functional somatotopy' representation of the finger in primary motor cortex.

Hybrid Power-Assisted Functional Electrical Stimulation to Improve Hemiparetic Upper-Extremity Function

The effect on spastic hemiparesis of a hybrid therapy consisting of functional electrical stimulation and block therapy was examined. Sixteen consecutively enrolled stroke patients who had spastic upper-extremity impairments more than 1 yr after stroke were recruited for this nonblinded randomized controlled trial. Patients underwent hybrid functional electrical stimulation therapy on their extensor carpi radialis longus and brevis, extensor digitorum communis, and extensor indicis proprius muscles once or twice a week for 4 mos after motor point blocks at the spastic finger flexor muscles. Surface electrodes picked up the electromyography signal and stimulated those muscles in proportion to the integrated electromyography signal obtained by the functional electrical stimulation device. The root mean square of the extensor carpi radialis longus and extensor digitorum communis maximum voluntary electromyography, active range of motion of wrist extension, finger extension, Modified Ashworth Scale, and two clinical tests were examined before and after training. Root mean square, active range of motion, Modified Ashworth Scale, and two clinical tests showed marked improvement in all patients as compared with the control subjects. The hybrid therapy was effective for patients with chronic spastic hemiparesis. Proprioceptional sensory feedback may have an important role in power-assisted functional electrical stimulation therapy.

Reversed extensor indicis proprius muscle and dorsal wrist pain

Reversed extensor indicis proprius muscle and dorsal wrist pain

Anatomical studies on the extensor pollicis et indicis accessorius muscle and the extensor indicis radialis muscle in Japanese.

Anatomical studies on the extensor pollicis et indicis accessorius and extensor indicis radialis muscles were conducted on 952 upper limbs from 476 Japanese adult cadavers. Each anomalous muscle occurred between the extensor pollicis longus proprius and extensor indicis proprius muscles in the dorsum of the forearm and hand. The extensor pollicis et indicis accessorius muscle was present in 13 of the limbs (1.4%). It was not coexistent with another anomalous muscle of the extensor digitorum profundus mass in 9 cases, and it was coexistent with that muscle in 4. The extensor indicis radialis muscle was present in 34 limbs (3.6%). It was accompanied by another anomaly of the extensor digitorum profundus mass in 5 cases, and not accompanied by that muscle in 29. The extensor pollicis et indicis accessorius and extensor indicis radialis muscles were innervated by the posterior interosseus nerve of the radial nerve. It seems that the former anomalous muscle supplies the extensor control of the thumb and index finger, and the latter one of the index finger only. Each anomalous muscle was considered to be differentiating on the radial side of the extensor digitorum profundus mass in humans.

The extensor medii proprius and anomalous extensor tendons to the long finger

The extensor medii proprius is a muscle analogous to the extensor indicis proprius in that it has a similar origin, but inserts into the long finger. The extensor indicis et medii communis muscle is an extensor indicis proprius muscle that splits to insert into both the index and long fingers. The extensor tendons to the fingers were dissected in 58 adult hands to determine the incidence and anatomy of the extensor medii proprius and extensor indicis et medii communis. The incidence of the extensor medii proprius was 10.3% and the incidence of the extensor indicis et medii communis was 3.4% in this series. The extensor medii proprius and extensor indicis proprius muscles had a common origin in all cases. The insertion of the extensor medii proprius into the dorsal aponeurosis was palmar and ulnar to the extensor digitorum communis of the long finger, but in one case, the extensor medii proprius inserted into the deep fibrous tissue proximal to the metacarpophalangeal joint. The tendon slip of the extensor indicis et medii communis inserting into the long finger did not insert into the dorsal aponeurosis, but into the deep fibrous tissue near the metacarpophalangeal joint. Both the extensor medii proprius and the extensor indicis et medii communis may represent evolutionary remnants. Awareness of their potential presence and anatomy should be helpful in extensor identification, repair, and transfer.

Prime mover muscle in finger lift or finger flexion reaction times: identification with transcranial magnetic stimulation

When recording the onset of the electromyographic (EMG) voluntary response in reaction time (RT) studies, the electrodes should be placed on the muscle which is first and foremost involved in executing the response. It is thus necessary to identify which is the prime mover muscle among active synergic muscles. This has been investigated for index finger lift or flexion RTs by delivering a magnetic stimulus to motor cortical areas prior to the subject's voluntary response. The EMG responses to the magnetic stimulus were selectively facilitated either in the extensor indicis proprius muscle (in index lift RTs) or in the first dorsal interosseous muscle (in index flexion RTs). These effects are robust and provide a method for identifying the prime mover muscle in voluntary movements.

An unusual cause of wrist pain

A young man with painful swelling over the dorsum of his wrist was found to be caused by an anomalous extensor indicis proprius muscle.