The lateral root of the ulnar nerve

In 158 brachial plexuses the origin of the fibers of the ulnar nerve-whether only from the medial or also from the lateral fascicle-was investigated. A lateral root was found in 56%. This lateral root may either be accompanied by fibers of the median nerve (type 1) or may run separately (type 2). Where this root crosses the medial root of the median nerve, either a small minority of fibers of the latter nerve may run behind the ulnar fibers (type a), or all median fibers are in front of them (type b). Considering the relation 56:44% between ulnar nerves with and without a lateral root both possibilities have to be considered as normal variations, none as a variety. In analogy to the term 'median loop' the term 'ulnaris loop' is suggested for specimens with a lateral root.     

Outcome following Nerve Repair of High Isolated Clean Sharp Injuries of the Ulnar Nerve

Objective

The detailed outcome of surgical repair of high isolated clean sharp (HICS) ulnar nerve lesions has become relevant in view of the recent development of distal nerve transfer. Our goal was to determine the outcome of HICS ulnar nerve repair in order to create a basis for the optimal management of these lesions.

Methods

High ulnar nerve lesions are defined as localized in the area ranging from the proximal forearm to the axilla just distal to the branching of the medial cord of the brachial plexus. A meta-analysis of the literature concerning high ulnar nerve injuries was performed. Additionally, a retrospective study of the outcome of nerve repair of HICS ulnar nerve injuries at our institution was performed. The Rotterdam Intrinsic Hand Myometer and the Rosén-Lundborg protocol were used.

Results

The literature review identified 46 papers. Many articles presented outcomes of mixed lesion groups consisting of combined ulnar and median nerves, or the outcome of high and low level injuries was pooled. In addition, outcome was expressed using different scoring systems. 40 patients with HICS ulnar nerve lesions were found with sufficient data for further analysis. In our institution, 15 patients had nerve repair with a median interval between trauma and reconstruction of 17 days (range 0–516). The mean score of the motor and sensory domain of the Rosen''s Scale instrument was 58% and 38% of the unaffected arm, respectively. Two-point discrimination never reached less then 12 mm.

Conclusion

From the literature, it was not possible to draw a definitive conclusion on outcome of surgical repair of HICS ulnar nerve lesions. Detailed neurological function assessment of our own patients showed that some ulnar nerve function returned. Intrinsic muscle strength recovery was generally poor. Based on this study, one might cautiously argue that repair strategies of HICS ulnar nerve lesions need to be improved.     

Surface landmarks to locate the thenar branch of the median nerve: an anatomical study

The thenar branch of the median nerve can be injured during carpal tunnel release. The purpose of this study was to identify surface landmarks to consistently predict the location of the thenar branch of the median nerve. Surface landmarks were marked and incised in 28 cadaveric hands. The incisions were made along the longitudinal line of the third web space and the horizontal cardinal line from the hamate hook to the ulnar border of the thumb. The origin of the thenar branch was determined in relation to these longitudinal and horizontal vectors. The origin of the thenar nerve branch was consistently observed in the radial proximal quadrant formed by the aforementioned longitudinal and horizontal vectors. The thenar branch origin was observed to be an average of 8.6 +/- 1.9 mm radial to the longitudinal axis along the third web space. The origin of the thenar branch was observed to be an average of 6.3 +/- 2.0 mm proximal to the horizontal axis between the hamate hook and the ulnar border of the thumb. The thenar branch was observed precisely at the intersection of the longitudinal vector from the second web space to the scaphoid tubercle and the horizontal vector from the hamate hook to the radial edge of the proximal metacarpophalangeal crease in all 28 cadaveric hands. On the basis of these 28 cadaveric dissections, the location of the thenar branch of the median nerve can be predicted by the intersection of the longitudinal vector from the second web space to the scaphoid tubercle and the horizontal vector from the hamate hook to the radial aspect of the metacarpophalangeal crease.     

Aneurysm of the median artery causing recurrent carpal tunnel syndrome and anatomic review

A patient is presented who had recurrent carpal tunnel syndrome symptoms in his left hand 1 year after having undergone release of the transverse carpal ligament. On exploration, this was found to be due to an aneurysm of a median artery and possibly scarring due to this compression around the branches of the bifurcated median nerve. This represents the first case in the literature to comment on (1) the absence of bilaterality of the anatomic finding and (2) carpal tunnel syndrome relative to median artery aneurysm. With this in mind, a plea is made for careful exploration of the carpal tunnel, maintaining an incision as far to the ulnar side of the median nerve as technically possible with thorough visualization of the contents of the tunnel and any anatomic variance involved. The incidence of the combination of aberrant median artery with high bifurcation of the median nerve is unknown, as is the incidence of aneurysm of the median artery.     

Comparison of median and radial nerve sensory latencies in the electrophysiological diagnosis of carpal tunnel syndrome

An electrophysiological diagnosis of carpal tunnel syndrome (CTS) was made on the basis of the median sensory nerve action potential (SNAP) alone in 79 of 161 (49.1%) symptomatic hands without electrophysiological evidence of a generalised peripheral neuropathy. Comparison of distal sensory latencies (DSLs) for the median and radial nerves yielded abnormal results in 17 of the remaining hands with normal median nerve DSLs, increasing the electrodiagnostic yield to 59.6%. Carpal tunnel decompression has been performed in seven of these hands, with abnormal intraoperative findings reported in two, while all improved clinically following surgery, substantiating the diagnosis of CTS. Although the technique described here would not appear to increase the electrodiagnostic yield more than comparison of DSLs for the median and ulnar nerves, which has been reported previously, it remains an affective, quick and simple procedure for increasing the sensitivity of the nerve conduction studies.     

Epineurial Window Is More Efficient in Attracting Axons than Simple Coaptation in a Sutureless (Cyanoacrylate-Bound) Model of End-to-Side Nerve Repair in the Rat Upper Limb: Functional and Morphometric Evidences and Review of the Literature

End-to-side nerve coaptation brings regenerating axons from the donor to the recipient nerve. Several techniques have been used to perform coaptation: microsurgical sutures with and without opening a window into the epi(peri)neurial connective tissue; among these, window techniques have been proven more effective in inducing axonal regeneration. The authors developed a sutureless model of end-to-side coaptation in the rat upper limb. In 19 adult Wistar rats, the median and the ulnar nerves of the left arm were approached from the axillary region, the median nerve transected and the proximal stump sutured to the pectoral muscle to prevent regeneration. Animals were then randomly divided in two experimental groups (7 animals each, 5 animals acting as control): Group 1: the distal stump of the transected median nerve was fixed to the ulnar nerve by applying cyanoacrylate solution; Group 2: a small epineurial window was opened into the epineurium of the ulnar nerve, caring to avoid damage to the nerve fibres; the distal stump of the transected median nerve was then fixed to the ulnar nerve by applying cyanoacrylate solution. The grasping test for functional evaluation was repeated every 10–11 weeks starting from week-15, up to the sacrifice (week 36). At week 36, the animals were sacrificed and the regenerated nerves harvested and processed for morphological investigations (high-resolution light microscopy as well as stereological and morphometrical analysis). This study shows that a) cyanoacrylate in end-to-side coaptation produces scarless axon regeneration without toxic effects; b) axonal regeneration and myelination occur even without opening an epineurial window, but c) the window is related to a larger number of regenerating fibres, especially myelinated and mature, and better functional outcomes.     

An Electrophysiological Study of Acute Tetrodotoxin Poisoning

To evaluate the electrophysiological changes in patients with acute tetrodotoxin (TTX) poisoning from ingestion of globefish (Tetraodontidae) patients exposed to TTX were compared with age-matched controls. The cohort of TTX-poisoning cases was clinically subdivided into mild, moderate, or severe cases. The motor nerve conduction velocity (MCV), sensory nerve conduction velocity (SCV), F-wave, H-reflex, and somatosensory-evoked potentials (SEP) of the median, ulnar, and common peroneal nerve (CPN) were determined using established techniques. Four of the 64 (6.3%) TTX-poisoning cases died and were omitted from the final analysis. The MCV and SCV of the median, ulnar, and CPN nerves in all the TTX-poisoning cases were significantly slower than the healthy controls. Severe cases of TTX poisoning had more significant reduction in nerve function. Thus, electroneurophysiological analysis could be used to determine the extent, course, and range of nerve system damage in patients with acute TTX poisoning.     

The 'loge de Guyon'. A contribution to the clinical anatomy of the human hand

In 40 hands of adults the 'loge de Guyon', a narrow bounded area within the proximal hypothenar region, has been dissected to realize an exact determination of the important characteristics of size. Beside measurements of the wall structures in the region of the pisiform bone, the hook of hamate and the entrances of the loge, variations of muscles and the position of the ulnar artery and nerve with their terminal branches have also been examined. The deep palmar branch of the ulnar artery crosses the rami of the ulnar nerve on the palmar side in 65% of cases. The branch of the artery crosses on the dorsal side in 30% and in 5% the ramus profundus of the ulnar artery runs between both terminal branches of the ulnar nerve. The clinical significance of the loge is emphasized, whereas the irregular nomenclature in the national and international literature is discussed in detail.     

The superior laryngeal nerve and the superior laryngeal artery

Length, diameter and anastomoses of the nervus vagus and its ganglion inferius were measured 44 halved heads. On the average, 8.65 fiber bundles of the vagus nerve leave the retro-olivary area. In the area of the jugular foramen is the near superior ganglion of the 10th cranial nerve. In this area were found 1.48 (mean value) anastomoses with the 9th cranial nerve. 11.34 mm below the margo terminalis sigmoidea branches off the ramus internus of the accessory nerve which has a length of 9.75 mm. Further anastomoses with the 10th cranial nerve were found. The inferior ganglion of the 10th nerve had a length of 25.47 mm and a diameter of 3.46 mm. Five mm below the ganglion the 10th nerve had a width of 2.9 and a thickness of 1.5 mm. The mean length of the superior sympathetic ganglion was 26.6 mm, its width 7.2 and its thickness 3.4 mm. In nearly all specimens anastomoses of the superior sympathetic ganglion with the ansa cervicalis profunda and the inferior ganglion of the 10th cranial nerve were found. The superior laryngeal nerve branches off about 36 mm below the margo terminalis sigmoidea. The width of this nerve was 1.9 mm, its thickness 0.8 mm on the right and 1.0 mm on the left side. The division in the internal and external rami was found about 21 mm below its origin. Between the n. vagus and thyreohyoid membrane the ramus internus had a length of 64 mm, the length of external ramus between the vagal nerve and the inferior pharyngeal constrictor muscle was 89 mm. Its mean length below the thyreopharyngeal part was 10.7 mm, 8.6 branchlets to the cricothyroid muscle were counted. The superior laryngeal artery had its origin in 80% of cases in the superior thyroideal artery, in 6.8% this vessel was a branch of the external carotid artery. Its average outer diameter was 1.23 mm on the right side and 1.39 mm on the left. The length of this vessel between its origin and the thyreohyoid membrane was 34 mm. In 7% on the right side and in 13% on the left, the superior laryngeal artery reached the larynx through a foramen thyreoideum. Ranges of diameters and lengths of vessels and nerves in the larynx are given.     

MR Neurography in Ulnar Neuropathy as Surrogate Parameter for the Presence of Disseminated Neuropathy

Purpose

Patients with ulnar neuropathy of unclear etiology occasionally present with lesion extension from elbow to upper arm level on MRI. This study investigated whether MRI thereby distinguishes multifocal neuropathy from focal-compressive neuropathy at the elbow.

Methods

This prospective study was approved by the institutional ethics committee and written informed consent was obtained from all participants. 122 patients with ulnar mononeuropathy of undetermined localization and etiology by clinical and electrophysiological examination were assessed by MRI at upper arm and elbow level using T2-weighted fat-saturated sequences at 3T. Twenty-one patients were identified with proximal ulnar nerve lesions and evaluated for findings suggestive of disseminated neuropathy (i) subclinical lesions in other nerves, (ii) unfavorable outcome after previous decompressive elbow surgery, and (iii) subsequent diagnosis of inflammatory or other disseminated neuropathy. Two groups served as controls for quantitative analysis of nerve-to-muscle signal intensity ratios: 20 subjects with typical focal ulnar neuropathy at the elbow and 20 healthy subjects.

Results

In the group of 21 patients with proximal ulnar nerve lesion extension, T2-w ulnar nerve signal was significantly (p<0.001) higher at upper arm level than in both control groups. A cut-off value of 1.92 for maximum nerve-to-muscle signal intensity ratio was found to be sensitive (86%) and specific (100%) to discriminate this group. Ten patients (48%) exhibited additional T2-w lesions in the median and/or radial nerve. Another ten (48%) had previously undergone elbow surgery without satisfying outcome. Clinical follow-up was available in 15 (71%) and revealed definitive diagnoses of multifocal neuropathy of various etiologies in four patients. In another eight, diagnoses could not yet be considered definitive but were consistent with multifocal neuropathy.

Conclusion

Proximal ulnar nerve T2 lesions at upper arm level are detected by MRI and indicate the presence of a non-focal disseminated neuropathy instead of a focal compressive neuropathy.     

Two distinct cervical N13 potentials are evoked by ulnar nerve stimulation

To investigate the dual nature of the posterior neck N13 potential, we attempted to establish the presence of a latency dissociation between caudal (cN13) and rostral (rN13) potentials on stimulating the ulnar nerve, in view of its lower radicular entry compared to the median nerve. SEPs were evaluated in 24 normal subjects after both median and ulnar nerve stimulation. cN13 was prominent in the lower cervical segments, and rN13 was localized mainly in the upper ones using anteroposterior and longitudinal bipolar montage, respectively. The N9-cN13 interpeak latency did not differ significantly from N9-rN13 when stimulating the median nerve. On the other hand, the N9-rN13 interpeak was significantly longer than the N9-cN13 interpeak when the ulnar nerve was stimulated. The rN13 presented the same latency as P13-P14 far-field potentials in 17 out of 24 ulnar nerves tested. Therefore, the ulnar nerve stimulation evokes two distinct posterior neck N13 potentials. It is widely accepted that the caudal N13 is a postsynaptic potential reflecting the activity of the dorsal horn interneurons in the lower cervical cord. We suggest that the rostral N13 is probably generated close to the cuneate nucleus, which partly contributes to the genesis of P13-P14 far-field potentials.     

Thenar and hypothenar muscles and their innervation by the ulnar and median nerves in the human hand.

The thenar and hypothenar muscles as well as their supplying nerves were analyzed with an improved dissecting method. Among the four thenar muscles, the m. abductor pollicis brevis (AbPB) has a separate muscle belly, whereas the m. opponens pollicis (OP), the superficial and deep heads of the flexor pollicis brevis (sFPB and dFPB), and the adductor pollicis (AdP) are fused with each other to make a single mass (deep thenar muscle group). These muscles are innervated by branches of the recurrent nerve and the accessory recurrent nerve from the median nerve as well as by terminal branches of the deep branch (ramus profundus) of the ulnar nerve. These three nerves frequently form a loop within the deep thenar muscle group (thenar loop), and a branch to the OP and one to deep parts of the sFPB often make a smaller loop (intrathenar loop), whereas the AbPB receives a separate nerve branch. Among the hypothenar muscle, the m. abductor digiti minimi and the m. flexor digiti minimi brevis are fused with each other, and their supplying nerves frequently form a loop in these muscles (intrahypothenar loop), whereas the m. opponens digiti minimi is separated from the others and receives a separate nerve branch. In the distribution pattern of supplying nerves to the thenar and hypothenar muscles, we find regularities in that they branch off in a regular manner from the ulnar and the median nerve, and that nerve branches to those muscles with fused bellies frequently communicate with each other to make loops.     

Novel model for end-neuroma formation in the amputated rabbit forelimb

Background

In our previous study, allogeneic-transplanted peripheral nerve segments preserved for one month in a polyphenol solution at 4°C could regenerate nerves in rodents demonstrated the same extent of nerve regeneration as isogeneic fresh nerve grafts. The present study investigated whether the same results could be obtained in a canine model.

Methods

A sciatic nerve was harvested from a male beagle dog, divided into fascicules of < 1.5 mm diameter, and stored in a polyphenol solution (1 mg/ml) for one month at 4°C. The nerve fascicles were transplanted into 10 female beagle dogs to bridge 3-cm right ulnar nerve gaps. In the left ulnar nerve in each dog, a 3-cm nerve segment was harvested, turned in the opposite direction, and sutured in situ. Starting one day before transplantation, the immunosuppressant FK506 was administered subcutaneously at doses of 0.1 mg/kg daily in four dogs (PA0.1 group), 0.05 mg/kg daily in four dogs (PA0.05 group), or 0.05 mg/kg every other day in two dogs (PA0.025 group). Twelve weeks after surgery, electrophysiological and morphological studies were performed to assess the regeneration of the right and left ulnar nerves. The data for the right ulnar nerve were expressed as percentages relative to the left ulnar nerve. Polymerase chain reaction (PCR) was used to identify the sex-determining region of the Y-chromosome (Sry) and β-actin to investigate whether cells of donor origin remained in the allogeneic nerve segments. FK506 concentration was measured in blood samples taken before the animals were killed.

Results

The total myelinated axon numbers and amplitudes of the muscle action potentials correlated significantly with the blood FK506 concentration. Few axons were observed in the allogeneic-transplanted nerve segments in the PA0.025 group. PCR showed clear Sry-specific bands in specimens from the PA0.1 and PA0.05 groups but not from the PA0.025 group.

Conclusions

Successful nerve regeneration was observed in the polyphenol-treated nerve allografts when transplanted in association with a therapeutic dose of FK506. The data indicate that polyphenols can protect nerve tissue from ischemic damage for one month; however, the effects of immune suppression seem insufficient to permit allogeneic transplantation of peripheral nerves in a canine model.     

The value of ulnar somatosensory evoked potentials (SEPs) in cervical myelopathy

In 57 patients with clinical signs and surgical documentation of compressive myelopathy, ulnar nerve somatosensory evoked potentials (SEPs) were more sensitive (with 74% abnormal) than either median or tibial nerve SEPs. The most frequent abnormalities were reduced or absent neck evoked responses and prolonged central conduction time. All subjects who had an SEP abnormality were identified by combined tibial and ulnar SEPs. Median nerve SEP added no additional information. Normal ulnar and tibial nerve SEPs were also able to exclude major cord damage in patients with cervical radiculopathy but little evidence of myelopathy.     

Somatotopy of human hand somatosensory cortex as studied in scalp EEG

We recorded somatosensory evoked potentials (SEPs) in scalp EEGs during stimulation of the median nerve, the ulnar nerve and the individual digits in 3 normal subjects and in 1 epilepsy patients. In this patient we also measured SEPs from chronically indwelling subdural grid electrodes during electrocorticography (ECoG). We applied dipole modelling techniques to study the 3-dimensional intracerebral locations and time activities of the neuronal sources underlying stimulation of different peripheral receptive fields. The sources underlying median nerve SEPs were located an average of 10.8 mm lateral inferior to those underlying ulnar nerve SEPs. Digit SEP sources showed a somatotopic arrangement from lateral inferior to medial superior in the order thumb, index finger, middle finger, ring finger and little finger, with some overlap or reversal for adjacent digits. The average distance between thumb and little finger was 12.5 mm. Thumb, index finger and middle finger were clustered around median nerve cortical representation, whereas ring finger and little finger were arranged around ulnar nerve cortex. In the epilepsy patient, the source localizations obtained in scalp EEGs showed good agreement with those on ECoGs. We conclude that SEPs recorded in scalp EEGs can be used to study functional topography of human somatosensory cortex non-invasively.     

Dermatomal and mixed nerve somatosensory evoked potentials in the diagnosis of neurogenic thoracic outlet syndrome

To evaluate the diagnostic utility of dermatomal and mixed nerve somatosensory evoked potentials (SEPs) in patients with thoracic outlet syndrome (TOS) and to compare their value with routine electrodiagnostic methods, we studied a group of 44 patients with neurogenic TOS and 30 healthy controls. In addition to bilateral median and ulnar SEPs, evoked potentials were recorded after stimulation of C6 and C8 dermatomes from the first and fifth digits, respectively. The patients were classified into 3 groups according to the nature of their clinical condition. The abnormality rate for both ulnar and C8 dermatomal SEPs was 100% in a small group of patients with severe neurological signs like atrophy. In groups of patients with lesser degrees of neurogenic damage, abnormality rates for ulnar and C8 dermatomal SEPs on affected limb(s) were 67 and 50%, respectively. Same abnormality rates were 25 and 18% in patients with only subjective symptoms. In patients with objective neurological signs, the major increase in sensitivity was with electromyography (EMG). Abnormalities of routine nerve conduction studies and F-wave latency were observed in patients with severe neurogenic damage. We concluded that the most useful tests in the diagnosis of neurogenic TOS are needle EMG and ulnar SEPs.     

Electrophysiological and histopathological changes in peripheral nerves of postnatally undernourished and rehabilitated young rhesus monkeys

Nerve condition velocity of ulnar and tibial nerves and qualitative histology of ulnar nerve were studied in young rhesus monkeys. Motor nerve condition velocity of both the nerves and amplitude of sensory response of ulnar nerve were significantly decreased in even moderate protein calorie malnourished (PCM) group of monkeys. Increased paranodal gap, segmental demyelination, thin myelinated fibres and prominent Schmidt Lanterman Clefts were also observed in PCM group. There was complete recovery in motor nerve conduction velocity in the nerves of both limbs while partial in amplitude of sensory response in proximal segment of ulnar nerve on nutritional rehabilitation of 10-12 weeks.     

Sensorimotor Modulation Differs with Load Type during Constant Finger Force or Position

During submaximal isometric contraction, there are two different load types: production of a constant force against a rigid restraint (force task), and maintenance of position against a constant load (position task). Previous studies reported that the time to task failure during a fatigue task was twice as long in the force task compared with the position task. Sensory feedback processing may contribute to these differences. The purpose of the current study was to determine the influence of load types during static muscle contraction tasks on the gating effect, i.e., attenuation of somatosensory-evoked potentials (SEPs) and the cortical silent period (cSP). Ten healthy subjects contracted their right first dorsal interosseus muscle by abducting their index finger for 90 s, to produce a constant force against a rigid restraint that was 20% of the maximum voluntary contraction (force task), or to maintain a constant position with 10° abduction of the metacarpophalangeal joint against the same load (position task). Somatosensory evoked potentials (SEPs) were recorded from C3′ by stimulating either the right ulnar or median nerve at the wrist while maintaining contraction. The cortical silent period (cSP) was also elicited by transcranial magnetic stimulation. Reduction of the amplitude of the P45 component of SEPs was significantly larger during the position task than during the force task and under control rest conditions when the ulnar nerve, but not the median nerve, was stimulated. The position task had a significantly shorter cSP duration than the force task. These results suggest the need for more proprioceptive information during the position task than the force task. The shorter duration of the cSP during the position task may be attributable to larger amplitude of heteronymous short latency reflexes. Sensorimotor modulations may differ with load type during constant finger force or position tasks.     

Development of the innervation pattern in the upper limb of staged human embryos

The upper limb nerves of 8 human embryos (Carnegie stages 13-21) were studied by reconstruction. In stage 13, upper limb nerves (C5-T1) extended from the spinal cord. In stage 14, these nerves united to form the nascent brachial plexus. In stages 16 and 17, the median nerve, the radial nerve and the ulnar nerve entered into the hand plate. In stages 20 and 21, the upper limb nerves were observed in an orientation and arrangement similar to those in the adult.