18218ournal ofNeurology, Neurosurgery, and Psychiatry 1995;59:182-184 SHORT REPORT J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.59.2.182 on 1 August 1995. Downloaded from Palmaris brevis spasm syndrome Georges Serratrice, Jean-Philippe Azulay, Jacques Serratrice, Jean Pouget Abstract in the palmaris brevis and abductor digiti Palmaris brevis spasm syndrome is a minimi muscles. The other muscles of the rare and benign condition of localised hand were normal. Motor unit potentials had muscular hyperactivity. In five men, the a normal configuration with 1 mV amplitude, hypothenar eminence underwent sponta- recurrent with 20 to 30 Hz frequency. An neous, irregular, tonic contractions of EMG was normal with voluntary contraction. the palmaris brevis muscle. An EMG Motor and sensory nerve velocities and ulnar showed spontaneous high frequency dis- F wave latency were normal. Carbamazepine charges of normal motor units, without was ineffective. Infiltration of the ulnar nerve evidence of neuropathy or of nerve com- at the wrist with lidocaine reduced the dis- pression. This syndrome resembles other charges but they were not abolished. Finally, restricted muscle hyperactivity syn- there was a dramatic improvement with dromes although there are some differ- phenytoin (200 mg/day). ences. Curiously, the palmaris brevis muscle is not under voluntary control. PATIENT 2 The mechanism of the syndrome could A 37 year old man complained of diffuse be an ephaptic transmission possibly sec- myalgia and exercise intolerance. For eight ondary to the transient and repeated months he had experienced difficulty in writ- stretching of the ulnar nerve superficial ing and had spontaneous, slightly painful, branch. In one patient a root compres- contractions in the right hypothenar emi- sion was the probable origin. nence. Spasms (fig 1) were spontaneous and irregular. Neurological examination was nor- (7 Neurol Neurosurg Psychiatry 1995;59: 182-184) mal and showed no weakness or amyotrophy. There was a diminished vibratory sensation in Keywords: palmaris brevis spasm; continuous muscle the feet. An EMG showed irregular dis- hyperactivity; myokimia charges of high frequency. Isolated potentials http://jnnp.bmj.com/ were normal in amplitude (0 5 to 1-5 mV), Palmaris brevis spasm is a rare muscular configuration, and duration, in the right pal- hyperactivity syndrome' 2 confined to a rudi- maris brevis and right abductor digiti minimi mentary muscle. The mechanism is unclear. and all the other intrinsic hand muscles were Five patients have been seen in different con- normal. Motor and sensory nerve conduction ditions. velocities and F wave latencies were normal. Results of routine laboratory tests including CSF and lactic acid showed no abnormalities. on September 25, 2021 by guest. Protected copyright. Case reports Magnetic resonance spectroscopy showed a PATIENT 1 delayed phosphocreatine recovery. Quadri- Immediately after surgery (for coxarthrosis, ceps muscle biopsy indicated a moderate type performed four months previously) a 76 year II fibre atrophy without any specific morpho- old man experienced paraesthesiae and logical changes. Baclofen was ineffective. hypoaesthesia in the left little finger and in the internal side of the fourth finger. During PATIENT 3 Cliniques des surgery, the had been on the A 62 year old man had a two Maladies du Systeme patient lying experienced nerveux et de right side and his left arm was fixed in abduc- month history of right C8 root pain and l'Appareil locomoteur, tion by a brace while his hand was dropping paraesthesiae radiating to the right little fin- Hopital de la Timone, loose. Since the operation the patient had ger. He had had a trauma of the neck when 13005 Marseille, France been complaining of spontaneous spasms in aged 40. There were spontaneous contrac- G Serratrice the left hypothenar eminence. Contractions tions and a dimple in the right hypothenar J-P Azulay were irregular without stereotyped duration eminence. There was a weakness of the long J Serratrice J Pouget or frequency. They occurred more often on extensor and flexor muscles of the fingers and Correspondence to: abduction of the left abductor digiti minimi a dorsal interossei amyotrophy. The stretch- Professor G Serratrice. muscle. Results of a neurological examination ing reflex of the right triceps muscle was Received 20 January 1995 were normal. Radiographs of the wrists were absent. An EMG showed high amplitude and in revised form 10 March 1995. normal. An EMG showed bursts of sponta- (8 mV) and frequency potentials in the right Accepted 16 March 1995 neous discharges during two to three seconds abductor digiti minimi muscle as well as in Palmaris brevis spasm syndrome 183 elbow. A cervical myelogram showed right J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.59.2.182 on 1 August 1995. Downloaded from .I. | . | : | C8 compression. s : s 8 Il : s . s .......r.-;Xr ... s . s PATIENT 4 si: ., .: | A 54 year old man complained of a two year :sX .sa IF *: history of paraesthesiae in both little fingers and in both fourth fingers. A year before he had had decompressive surgery of the left ulnar nerve at the elbow without any improvement. He experienced paraesthesiae and spontaneous spasms in both hypothenar eminences. Contractions occurred more often on abduction of the abductor digiti minimi (fig 2). There was hypoaesthesia in both little fingers and in the internal side of both fourth fingers. An EMG showed high amplitude and high frequency potentials in the right (14 mV) and left (16 mV) abductor digiti minimi muscles. Motor nerve conduction velocities and F wave latencies were normal. The amplitude of sensory potentials was slightly decreased in the ulnar nerves. He was treated with phenytoin (200 mg/day) without improvement. PATIENT 5 A 40 year old man complained of a six month history of spontaneous and irregular contrac- tion in the ulnar side of both hands. Tonic contractions and a dimple in both hypothenar 11g; :#. :' . __ 111 :.:. xj, ;.,d<<jja _! | abi =AG2 _* R ... eminences were induced by a triggering ges- Figure I Patient 2; right hypothenar eminence dimple. ture, when the patient put the ulnar side of his hand on a table pressing on the pisiform the finger extensors. The muscles of the arm (sesamoid bone in the tendon of the flexor were normal. Ulnar nerve motor conduction carpis ulnaris) or during wrist flexion. The velocity was 65 m/s and sensory conduction spasm was aggravated after a blow on his *= .:&:':S i X. i i °'ss ............--l;J9 l I | .: w . velocity was 42 mIs. At the elbow, motor con- right forearm a month before. Neurological g . :@g: - ! : . :.:: i - . l . , duction was 36 examination was normal. An EMG showed *x i 111>_ I *;: velocity m/s. Radiographs showed cervical osteoarthritis and a normal high amplitude (10 mV) and irregular fre- quency potentials in both palmaris brevis muscles. Motor and sensory nerve velocities Figure 2 Patient 4; were normal. contractions occuring on http://jnnp.bmj.com/ abduction. Discussion The palmaris brevis muscle is a small, quadri- lateral, thin muscle located under the skin of > . the hypothenar eminence. Parallel and trans- w w : t. w : .|. :f verse fibre bundles arise from the ulnar side 1: .t. Ey. of the palmaris aponeurosis. The muscle end- on September 25, 2021 by guest. Protected copyright. :lw. .> ing is located in the deep derma at the medial :. R .: .2: *;.§. #2. fok side of the hand. Thus the muscle action is to crease and to ripple the skin, giving an *S x .X hypothenar eminence dimple. Interestingly, .i,¢ ..; the palmaris brevis muscle is not under vol- untary control and its contraction is strictly involuntary. The ulnar nerve divides into superficial and deep terminal branches and the superficial branch extends distally. A small twig supplies the palmaris brevis mus- cle. At the distal border of this muscle the A superficial branch is divided into palmar digi- tal branches for the ulnar side of the little fin- ger and the fourth interdigital space. It is important to note that this ulnar superficial branch has both motor and sensory functions whereas the twig supplying the palmaris bre- vis muscle is a motor nerve only. Theoretically a nerve entrapment causes motor and sensory disturbances. 184 Serratrice, Azulay, Serratrice, Pouget The symptoms of palmaris brevis muscle ulnar nerve at the wrist resulted in complete J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.59.2.182 on 1 August 1995. Downloaded from spasm are similar in three other reported nerve block abolishing both spasm and spon- patients' 2 and in our five patients but there taneous discharges whereas in patient 1 of are a few differences. The main clinical char- our series, discharges were only reduced by acteristics are (a) frequency in older men; (b) infiltrations. Carbamazepine was ineffective isolated contractions of the palmaris brevis in our patients and baclofen was ineffective in muscle; (c) spontaneous, brisk, irregular tonic patient 2. On the other hand there was a dra- contractions; (d) dimpling in the ulnar side of matic improvement with phenytoin in patient the hand without stereotyped duration or fre- 1 of our series. quency; (e) usually no triggering factors; the The mechanism of the spasm restricted to patient is unable to initiate the contraction at the palmaris brevis muscle is unclear and the will and the contractions start and stop with- aetiology could be different in each of our five out any apparent cause. The voluntary con- patients. In patient 1, the spontaneous dis- traction of the little finger (patient 4) or a charges arose in areas of hypothetical func- pressure on the pisiform (patient 5) could tional focal damage in a stretched peripheral sometimes trigger the dimpling; (J) benign nerve, possibly through ephaptic transmis- evolution for several years; (g) aggravation sion. In patient 2, the exact site of the abnor- under stress or excitement, decrease at rest or mal spontaneous discharges is unknown.