A 22-year-old man showed electrophysiological evidence of an ulnar-tomedian nerve communication involving only sensory fibers. The nerve action potentials evoked by stimulation of the middle finger (ulnar side) and the ring finger (radial side) digital nerves were propagated with the median nerve at the wrist and the ulnar nerve at the elbow. He was the only subject among 30 studied with this abnormality. Key words: nerve anastomosis innervation anomaly MUSCLE & NERVE 13:654-656 1990
FOREARM ULNAR-TO=MEDIANNERVE ANASTOMOSlS OF SENSORY AXONS HANNS C. HOPF, MD
A
ma1 to the proximal interphalangeal joint and the median-to-ulnar nerve communication in the anode 20 mm distally. The evoked nerve potential forearm (Martin-Gruber a n a s t o m o s i ~ ~is~ ~ob) was served in 6% to 31% of a normal p o p ~ l a t i o n . ~ , ~ ~ ' ~ recorded by needle electrodes with the recording electrode placed near the nerve and the The findings of Crutchfield and Gutmann' sugreference subcutaneously over the radial and ulgest an autosomal dominant inheritance of the nar aspects of the respective joints. The motor reanomaly which probably accounts for varying mansponses of the thenar and the hypothenar muscles ifestation rates within different ethnic group^.^ to stimulation of the median and ulnar nerves at In contrast, ulnar-to-median nerve communithe wrist and the elbow were recorded by surface cation in the forearm is rare, having been reelectrodes. ported on only three occasions on the basis of electrophysiological studies.6-8 A case is reported of this unusual crossover involving only sensory fiRESULTS bers. Following ulnar nerve block at the elbow by 5 mL of 1% mepivacaine, sensory loss occurred in the MATERIALS AND METHODS 5th and the 4th fingers and at the ulnar half of The findings in a 22-year-old man were discovthe 3rd finger, as was observed in another 4 of the ered incidentally during serial investigations on 30 tested subjects. Conduction studies were perthe sensory distribution of the ulnar nerve of the formed after recovery from the nerve block. Stimhand in 30 healthy subjects. Sensory conduction ulation of the digital nerves of the 4th finger (rawas studied by stimulating the volar digital nerves dial side) and of the 3rd finger (ulnar side) evoked of the middle and ring fingers and recording median nerve potentials of 10 and 15 FV, respecfrom the ulnar and median nerves at the wrist and tively, at the wrist but no detectable ulnar nerve the elbow. Rectangular pulses of 0.1 msec duraresponses (Fig. 1). At the elbow there were ulnar tion and supramaximal intensity were applied via nerve potentials of 7 and 10 FV, respectively, but needle electrodes with the cathode placed proxino median nerve responses (Fig. 1). Motor conduction studies were normal (Fig. 2). T h e 2.0 mV response from the thenar recording to ulnar nerve stimulation at wrist and elbow is From the Neurologische Universitatsklinik, Mainz. Federal Republic of likely due to a volume conducted adductor pollicis Germany. activation. A motor axon contribution of an ulnarAddress correspondence to Dr. Hopf, Neurologische Universitatsklinik, to-median nerve anastomosis can be excluded, as Langenbeckstrasse 1, D-6500 Mainz, Federal Republic of Germany. there was no difference between the potentials Accepted for publication September 10, 1989. evoked at the wrist and elbow. CCC 0148-639W90/070654-03 $04.00 This pattern of anomalous innervation may ac0 1990 John Wiley & Sons, Inc
654
Ulnar-to-Median Anastomosis
MUSCLE & NERVE
July 1990
a
I
b
I .\
’
FIGURE 1. Sensory nerve action potentialsfrom ulnar and median nerves to stimulation of the middle finger radial side. Recording from median (a) and ulnar (b) nerves at the wrist (upper two traces) and elbow (bottom traces).
count for an atypical distribution of sensory disturbances occasionally seen in carpal tunnel syndrome. DISCUSSION
The sensory nerve action potential evoked by digital nerve excitation was propagated by the median nerve at the wrist and the ulnar nerve at the elbow, demonstrating an ulnar-to-median nerve anastomosis involving sensory fibers without evidence of motor axon involvement. Similar anastomoses observed in 3 prior cases involved primarily motor fibers.
I
\
\ lb
-J\
Marinacci’ was the first to describe this rare condition and in credit to him it may be called Marinacci-anastomosis. His patient, following median nerve trauma at the forearm, developed denervation of forearm flexor muscles usually supplied by the median nerve, but the hand muscles remained unaffected. Motor fibers to the thenar muscles were excitable either at the wrist in the median nerve or at the elbow in the ulnar nerve. An “almost normal” sensation at the hand suggested that afferent fibers also traveled with the anastomosis. The patient of Komar et a16 experienced loss of perspiration and only partial impairment of hand sensation and thenar muscle func-
I
\
r
3a
V
V
FIGURE 2. Motor responses evoked by ulnar and median nerve stimulation. Recordings from thenar (a) and hypothenar (b) muscles to stimulation of the ulnar (la,b and 2a,b) and median (3a,b and 4a,b) nerves at the wrist (la,b and 3a,b) and elbow (2a,b and 4a,b).
Ulnar-to-Median Anastomosis
MUSCLE & NERVE
July 1990
655
tion after complete median nerve transsection 5 cm above the elbow. A 15 mV thenar muscle response was evoked from the ulnar nerve at the elbow but not at the wrist. Streib's' case had a 4.9 mV smaller thenar muscle response to median
nerve stimulation at the elbow than to stimulation at the wrist. The thenar response to ulnar nerve stimulation at the elbow was 6.6 mV larger than to stimulation at the wrist. The digital nerve potential distribution was normal.
REFERENCES 1. Crutchfield CA, Gutmann L: Hereditary aspects of median-ulnar nerve communications. J Neurol Neurosurg Psychiat 1980;.43:53-55. 2. Gruber W: Uber die Verbindung des Nervus medianus mit dem Nervus ulnaris am Unterarm des Menschen und der Saugetiere. Arch Anat Physiol Wkewchuft Med 1870; 37~501-522. 3. Hopf HC, Hense W: Anomalien der motorischen Innervation an der Hand. Z EEG-EMG 1974; 5:220-224. 4. Kimura J, Murphy MJ, Varda DJ: Electrophysiological study of anomalous innervation of intrinsic hand muscles. Arch Neurol 1976; 33:842-844. 5. Kimura J, Ayyar DR: The hand neural communication between the ulnar and median nerves: Electrophysiological detection. Electrmyogr clin Neurophysiol 1984; 24 :409 -4 14. 6. K6mir J, Szegviri M, Gloviczky Z, Szintio A: Traumati-
656
Ulnar-to-Median Anastomosis
scher Durchschnitt des N. medianus ohne komplette motorische Parese: Martin-Grubersche Anastomose. Neruenarzt 1978; 49:697-699. 7. Marinacci A: The problem of unusual anomalous innervation of hand muscles: The value of electrodiagnosis in its evaluation. Bull Los Angeles Neurol Soc 1964; 29:133- 142. 8. Streib EW: Ulnar-to-median anastomosis in the forearm: Electromyographic studies. Neurology 1979; 29: 15341537. 9. Thomson A: Frequency and arrangement of communication between the median (or anterior interosseus) and ulnar nerves in the forearm. J Anat Physiol 1893; 27:192194. 10. Wilbourn AJ, Lambert EH: The forearm median-to-ulnar nerve communication: Electrodiagnostic aspects. (Abstract) Neurology 1976; 26:368.
MUSCLE & NERVE
July 1990
FOREARM ULNAR-TO=MEDIANNERVE ANASTOMOSlS OF SENSORY AXONS HANNS C. HOPF, MD
A
ma1 to the proximal interphalangeal joint and the median-to-ulnar nerve communication in the anode 20 mm distally. The evoked nerve potential forearm (Martin-Gruber a n a s t o m o s i ~ ~is~ ~ob) was served in 6% to 31% of a normal p o p ~ l a t i o n . ~ , ~ ~ ' ~ recorded by needle electrodes with the recording electrode placed near the nerve and the The findings of Crutchfield and Gutmann' sugreference subcutaneously over the radial and ulgest an autosomal dominant inheritance of the nar aspects of the respective joints. The motor reanomaly which probably accounts for varying mansponses of the thenar and the hypothenar muscles ifestation rates within different ethnic group^.^ to stimulation of the median and ulnar nerves at In contrast, ulnar-to-median nerve communithe wrist and the elbow were recorded by surface cation in the forearm is rare, having been reelectrodes. ported on only three occasions on the basis of electrophysiological studies.6-8 A case is reported of this unusual crossover involving only sensory fiRESULTS bers. Following ulnar nerve block at the elbow by 5 mL of 1% mepivacaine, sensory loss occurred in the MATERIALS AND METHODS 5th and the 4th fingers and at the ulnar half of The findings in a 22-year-old man were discovthe 3rd finger, as was observed in another 4 of the ered incidentally during serial investigations on 30 tested subjects. Conduction studies were perthe sensory distribution of the ulnar nerve of the formed after recovery from the nerve block. Stimhand in 30 healthy subjects. Sensory conduction ulation of the digital nerves of the 4th finger (rawas studied by stimulating the volar digital nerves dial side) and of the 3rd finger (ulnar side) evoked of the middle and ring fingers and recording median nerve potentials of 10 and 15 FV, respecfrom the ulnar and median nerves at the wrist and tively, at the wrist but no detectable ulnar nerve the elbow. Rectangular pulses of 0.1 msec duraresponses (Fig. 1). At the elbow there were ulnar tion and supramaximal intensity were applied via nerve potentials of 7 and 10 FV, respectively, but needle electrodes with the cathode placed proxino median nerve responses (Fig. 1). Motor conduction studies were normal (Fig. 2). T h e 2.0 mV response from the thenar recording to ulnar nerve stimulation at wrist and elbow is From the Neurologische Universitatsklinik, Mainz. Federal Republic of likely due to a volume conducted adductor pollicis Germany. activation. A motor axon contribution of an ulnarAddress correspondence to Dr. Hopf, Neurologische Universitatsklinik, to-median nerve anastomosis can be excluded, as Langenbeckstrasse 1, D-6500 Mainz, Federal Republic of Germany. there was no difference between the potentials Accepted for publication September 10, 1989. evoked at the wrist and elbow. CCC 0148-639W90/070654-03 $04.00 This pattern of anomalous innervation may ac0 1990 John Wiley & Sons, Inc
654
Ulnar-to-Median Anastomosis
MUSCLE & NERVE
July 1990
a
I
b
I .\
’
FIGURE 1. Sensory nerve action potentialsfrom ulnar and median nerves to stimulation of the middle finger radial side. Recording from median (a) and ulnar (b) nerves at the wrist (upper two traces) and elbow (bottom traces).
count for an atypical distribution of sensory disturbances occasionally seen in carpal tunnel syndrome. DISCUSSION
The sensory nerve action potential evoked by digital nerve excitation was propagated by the median nerve at the wrist and the ulnar nerve at the elbow, demonstrating an ulnar-to-median nerve anastomosis involving sensory fibers without evidence of motor axon involvement. Similar anastomoses observed in 3 prior cases involved primarily motor fibers.
I
\
\ lb
-J\
Marinacci’ was the first to describe this rare condition and in credit to him it may be called Marinacci-anastomosis. His patient, following median nerve trauma at the forearm, developed denervation of forearm flexor muscles usually supplied by the median nerve, but the hand muscles remained unaffected. Motor fibers to the thenar muscles were excitable either at the wrist in the median nerve or at the elbow in the ulnar nerve. An “almost normal” sensation at the hand suggested that afferent fibers also traveled with the anastomosis. The patient of Komar et a16 experienced loss of perspiration and only partial impairment of hand sensation and thenar muscle func-
I
\
r
3a
V
V
FIGURE 2. Motor responses evoked by ulnar and median nerve stimulation. Recordings from thenar (a) and hypothenar (b) muscles to stimulation of the ulnar (la,b and 2a,b) and median (3a,b and 4a,b) nerves at the wrist (la,b and 3a,b) and elbow (2a,b and 4a,b).
Ulnar-to-Median Anastomosis
MUSCLE & NERVE
July 1990
655
tion after complete median nerve transsection 5 cm above the elbow. A 15 mV thenar muscle response was evoked from the ulnar nerve at the elbow but not at the wrist. Streib's' case had a 4.9 mV smaller thenar muscle response to median
nerve stimulation at the elbow than to stimulation at the wrist. The thenar response to ulnar nerve stimulation at the elbow was 6.6 mV larger than to stimulation at the wrist. The digital nerve potential distribution was normal.
REFERENCES 1. Crutchfield CA, Gutmann L: Hereditary aspects of median-ulnar nerve communications. J Neurol Neurosurg Psychiat 1980;.43:53-55. 2. Gruber W: Uber die Verbindung des Nervus medianus mit dem Nervus ulnaris am Unterarm des Menschen und der Saugetiere. Arch Anat Physiol Wkewchuft Med 1870; 37~501-522. 3. Hopf HC, Hense W: Anomalien der motorischen Innervation an der Hand. Z EEG-EMG 1974; 5:220-224. 4. Kimura J, Murphy MJ, Varda DJ: Electrophysiological study of anomalous innervation of intrinsic hand muscles. Arch Neurol 1976; 33:842-844. 5. Kimura J, Ayyar DR: The hand neural communication between the ulnar and median nerves: Electrophysiological detection. Electrmyogr clin Neurophysiol 1984; 24 :409 -4 14. 6. K6mir J, Szegviri M, Gloviczky Z, Szintio A: Traumati-
656
Ulnar-to-Median Anastomosis
scher Durchschnitt des N. medianus ohne komplette motorische Parese: Martin-Grubersche Anastomose. Neruenarzt 1978; 49:697-699. 7. Marinacci A: The problem of unusual anomalous innervation of hand muscles: The value of electrodiagnosis in its evaluation. Bull Los Angeles Neurol Soc 1964; 29:133- 142. 8. Streib EW: Ulnar-to-median anastomosis in the forearm: Electromyographic studies. Neurology 1979; 29: 15341537. 9. Thomson A: Frequency and arrangement of communication between the median (or anterior interosseus) and ulnar nerves in the forearm. J Anat Physiol 1893; 27:192194. 10. Wilbourn AJ, Lambert EH: The forearm median-to-ulnar nerve communication: Electrodiagnostic aspects. (Abstract) Neurology 1976; 26:368.
MUSCLE & NERVE
July 1990
