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Isolated sensory impairment of the thumb due to an intraneural ganglion cyst in the median nerve
ISOLATED SENSORY IMPAIRMENT OF THE THUMB DUE TO AN INTRANEURAL GANGLION CYST IN THE MEDIAN NERVE S. J A R A D E H , J. R. S A N G E R and E. F. M A A S
From the Departments of Neurology and Plastic and Reconstructive Surgery, Medical College of Wisconsin, Milwaukee, Wisconsin, USA We describe an unusual case of digital neuropathy of the thumb due to compression of the median nerve in the distal forearm by an extruded ganglion cyst originating from the radio-scaphoid joint of the wrist. ElectrophysiologicaHy, both conduction slowing and block of median motor and sensory axons were present across the cyst. These changes improved after surgery.
Journal of Hand Surgery (British and European Volume, 1995) 20B." 4." 475-478 Table 1--Nerve conduction studies
Localized numbness of the thumb is rare and is almost always due to digital nerve entrapment in the hand (Dawson et al, 1990). We report a case of neuropathy of the thumb due to compression of the median nerve in the distal forearm by an extruded wrist ganglion.
Latency (msec) Median sensory WR-D2 R/L WR-D1 R/L MP-WR R/L Radial sensory WR-D1 R/L Ulnar sensory MP-WR R/L Median motor
CASE REPORT A 42-year-old man noted the sudden onset of numbness and paraesthesia over the pulp of his left thumb. The symptoms remained unchanged over the next week. Pin-prick perception was abnormal in the palmar skin of the left thumb. There was no muscular weakness. Phalen's manoeuvre was negative. Tinel's sign was positive over the wrist. During forceful wrist extension, a small, round, relatively mobile and non-collapsible mass became apparent near the palmaris longus tendon (Fig 1). Median and radial sensory nerve conduction studies were done antidromically. Table 1 summarizes the results of nerve conduction studies. The antidromic median sensory nerve action potential (SNAP) amplitude was significantly reduced in the thumb, while the radial digital SNAP was normal. The median motor distal latency was mildly prolonged. Other values were normal for our laboratory. The next step was to perform median nerve conduc-
Amplitude (mV)
2.8/2.9 2.5/2.5 2.0/2.0
0.040/0.035 0.022/0.011 0.075/0.065
2.3/2.4
0.016/0.017
1.7/1.7 4.1/4.9
0.040/0.035 12.5/6.5
DI =Digit 1; D2-Digit 2; WR=Wrist; MP=Midpalm.
Table 2--Nerve conduction studies with inching (pre-operative/postoperative)
Median sensory--Digit 1 Point A B C D E Median mixed--Midpalm Point A B C D E F Median motor--Thenar Point A B C D E
Latency (msec)
Amplitude
3.5/3.5 3.2/3.1 2.8/2.7 2.6/2.3 2.3/*
0.007/0.010 0.007/0.010 0.0012/0.011 0.0012/0.013 0.0011/*
3.5/3.7 3.8/4.1 4.4/4.6 4.7/5.0 4.9/5.5 5.1/* .
0.043/0.052 0.040/0.043 0.023/0.034 0.021/0.025 0.018/0.022 0.018/*
4.9/4.5 4.6/4.1 3.3/3.4 2.9/3.1 */2.5
6.8/6.5 6.7/6.6 7.1/6.6 7.0/6.5 */5.6
(my)
*Not performed.
Fig 1
tion studies using a modified inching technique (Kimura, 1979; Fig 2). Three parameters were used. First, median SNAPs were recorded at the thumb while stimulating antidromically proximal to the wrist (point A). The cathode was then moved distally in increments of 2 cm and the latencies recorded. Secondly, the median nerve mixed fibres were stimulated distally at the same points
Appearance of the lesion near the left wrist (arrow). 475
476
THE JOURNAL OF HAND SURGERYVOL. 20B No. 4 AUGUST 1995
and motor fibre stimulation. The evoked amplitudes dropped significantly across the same segment in all three parameters. Needle electromyography revealed reduced recruitment in the abductor pollicis brevis muscle, but normal insertional activity and motor unit action potentials. A magnetic resonance imaging study was obtained using coronal, axial and sagittal images. This confirmed a 2 cm mass with multiple septations intimately related to the median nerve. On the T 1-weighted images, the mass appeared similar in density to muscle, and on T2-weighted images, similar to muscle and fat. An ultrasound study was also done, which confirmed that the mass was largely cystic in view of throughtransmission and lack of internal echoes. Over the next few weeks, the patient noticed an increase in both the size of the lesion and thumb paraesthesiae. During surgery, the median nerve appeared normal except for a 2.5 cm area of cystic enlargement just proximal to the carpal tunnel. Extending from the cystic mass was a stalk which passed below the flexor retinaculum and entered the radiocarpal joint (Fig 4). This was first isolated and transected. It revealed clear synovial fluid (Fig 5) and the point of entry into the radio-carpal joint was excised. Using an operating microscope, interfascicular dissection was begun in the nerve proximal to the mass, proceeding into it, and carefully separating the fascicles. Several of these were extremely attenuated, but were in continuity. As the dissection proceeded, areas of extremely thin fibrous walled cavities filled with gelatinous material were entered. Multiple cavities within the nerve were decompressed. The entire lesion could not
[ D C B A Fig 2
Electrode placement across the median nerve to perform the inching study as explained in the text. The shaded zone represents the area of sensory loss.
while recording the nerve action potentials at the elbow. Thirdly, thenar compound muscle action potentials were recorded after stimulation at points A, B, and C. The results are shown at the top of Figure 3. As can be seen, the latencies showed significant slowing across the B-C segment overlying the lesion mainly after mixed
Pre-op Median Mixed
Pre-op Median Sensory
Pre-op Median Motor
A 8 C
c
~
D
~
~
c
D
D
D
E
~t E F
o~s 1:o
20uV ~_ 1msec
lls
ms
15
0.'5
20 uv / 1rnsec
1.'5
Post-op Median Mixed
Post-op Median Sensory
o:s 11o 1~5
5rnV~ N\A* 2msec
ms
ms
Post-op Median Motor A B
C C
D
__.._.__.,/v----~ °
E
E
F
E
2OuV - N \ A I¢ 1 rnsec
Fig 3
01S
110 ms
lls
20uV -N\A* 1msec
0
015 I~0 £s ms
E
5mY [ _ 2msec
01s
1~o 1;s ms
Results of the inching study before (top traces) and after surgery (bottom traces). The histograms illustrate the latency differences between successive sites. Note the pre-operative reduction in the area and the increase in the latency of the median-evoked responses across the B-C segment overlying the lesion.
477
GANGLION IN MEDIAN NERVE
Fig 4
The median nerve at exploration. The instrument is beneath the stalk of ganglion where it enters the nerve (arrow). Note the cystic appearance.
Fig 5
A droplet of clear gelatinous material (arrow) emerging from the cystic lesion in the nerve. Multiple loculated areas containing similar fluid were noted.
be excised without risk of damaging nerve fascicles and for this reason the area was marsupialized and left open. After the operation, the patient had pain and hypoaesthesia over the palmar aspect of the whole thumb that resolved in 1 week. Post-operative nerve conduction studies showed significant improvement of the conduction block and slowing 4 months after the surgery (Fig 3). There was mild but insignificant prolongation of the total median sensory and mixed latencies across the whole A-E segment (Table 2). DISCUSSION This case illustrates an unusual aetiology of thumb involvement in a median mononeuropathy. The reduced median SNAP amplitude to the thumb and the prolonged median motor distal latency along with a positive Tinel's sign suggested carpal tunnel syndrome. However,
the preservation of a normal median mid-palmar orthodromic response made us question the diagnosis (Kimura, 1979). The modified inching technique demonstrated both significant conduction slowing and amplitude drop across a discrete segment overlying the lesion and was consistent with focal demyelination. A review of the fascicular topography of the median nerve in the distal forearm shows that the thenar muscular branch ~nd the cutaneous fibres from the thumb and lateral palm join together on the radial side of the median nerve in the distal forearm (Sunderland, 1978). Accordingly, a laterally located lesion in the distal forearm may present with isolated involvement of these fibres. In contrast to this case, ganglion cysts at the wrist have selectively affected the palmar cutaneous branch and spared the cutaneous digital fibres (Buckmiller and Richard, 1987; Gessini et al, 1983). Another unusual feature of this case is the aetiology of the compression. Although the cystic appearance and the location of the mass resembled cysts of the flexor tendon sheath (Buckmiller and Richard, 1987), the rapid onset of symptoms and the increase in size suggested an aggressive intraneurat or neoplastic process. The cyst originated from the radio-carpal joint, entered the nerve, expanded proximally, and infiltrated along fascicles, distending particularly the lateral aspect of the median nerve. Intraneural ganglion cysts are uncommon and those involving the median nerve are exceptional. Hartwell (1901) was the first to describe a case, but his patient had a high lesion located medial to the biceps muscle. During surgery in our case, the nerve enlargement contained thick fluid but otherwise appeared normal. Microscopic examination of one nerve fascicle showed Schwann cell and fibroblast proliferation, extensive demyelination and some axonal degeneration. Our electrophysiologic findings and post-operative recovery are also consistent with focal demyelination. A series from France (Allieu and Cenac, 1989) included one patient with a median nerve pseudocyst proximal to the pronator teres arch. Electrophysiological data were not explicit. These authors emphasized the peculiar lack of median nerve pseudocysts near the carpal tunnel. We have not found similar reports in our literature review and wish to add our case to the list of causes of median neuropathy affecting the thumb.
References ALLIEU, Y. and CENAC, P. E. (1989). Peripheral nerve mucoid degeneration of the upper extremity. Journal of Hand Surgery, 14A: 2(1): 189-194. BUCKMILLER, J. F. and RICHARD, T. A. (1987). Isolated compression neuropathy of the palmar cutaneous branch of the median nerve. Journal of Hand Surgery, 12A: 1: 97-99. DAWSON, D. M., HALLETT, M. and MILLENDER, L. H. (1990). Entrapment Neuropathies, 2nd Edn. Boston, Little, Brown, 253-267. GESSINI, L., JANDOLO, B., PIETRANGELI, A. and SENESE, A. (1983). Compression of the palmar cutaneous nerve by ganglions of the wrist. Journal of Neurosurgical Sciences, 27: 241-243.
478 H A R T W E L L , A. S. (1901). Cystic tumor of median nerve: Operation: Restoration of function. Boston Medical and Surgical Journal, 144: 582-583. K I M U R A , J. (1979). The carpal tunnel syndrome: Localization of conduction abnormalities within the distal segment of the median nerve. Brain, 102: 619 635.
T H E J O U R N A L O F H A N D SURGERY VOL. 20B No. 4 A U G U S T 1995 S U N D E R L A N D , S. (1978). Nerves and Nerve Injuries, 2nd Edn, Edinburgh, Churchill Livingstone, 672-677.
Accepted: 9 February 1995 Safwan Jaradeh MD, Department of Neurology, MCW Clinic at Froedtert, 9200 West, Wisconsin Avenue, Milwaukee, Wisconsin 53226, USA. © 1995 The British Society for Surgery of the Hand
From the Departments of Neurology and Plastic and Reconstructive Surgery, Medical College of Wisconsin, Milwaukee, Wisconsin, USA We describe an unusual case of digital neuropathy of the thumb due to compression of the median nerve in the distal forearm by an extruded ganglion cyst originating from the radio-scaphoid joint of the wrist. ElectrophysiologicaHy, both conduction slowing and block of median motor and sensory axons were present across the cyst. These changes improved after surgery.
Journal of Hand Surgery (British and European Volume, 1995) 20B." 4." 475-478 Table 1--Nerve conduction studies
Localized numbness of the thumb is rare and is almost always due to digital nerve entrapment in the hand (Dawson et al, 1990). We report a case of neuropathy of the thumb due to compression of the median nerve in the distal forearm by an extruded wrist ganglion.
Latency (msec) Median sensory WR-D2 R/L WR-D1 R/L MP-WR R/L Radial sensory WR-D1 R/L Ulnar sensory MP-WR R/L Median motor
CASE REPORT A 42-year-old man noted the sudden onset of numbness and paraesthesia over the pulp of his left thumb. The symptoms remained unchanged over the next week. Pin-prick perception was abnormal in the palmar skin of the left thumb. There was no muscular weakness. Phalen's manoeuvre was negative. Tinel's sign was positive over the wrist. During forceful wrist extension, a small, round, relatively mobile and non-collapsible mass became apparent near the palmaris longus tendon (Fig 1). Median and radial sensory nerve conduction studies were done antidromically. Table 1 summarizes the results of nerve conduction studies. The antidromic median sensory nerve action potential (SNAP) amplitude was significantly reduced in the thumb, while the radial digital SNAP was normal. The median motor distal latency was mildly prolonged. Other values were normal for our laboratory. The next step was to perform median nerve conduc-
Amplitude (mV)
2.8/2.9 2.5/2.5 2.0/2.0
0.040/0.035 0.022/0.011 0.075/0.065
2.3/2.4
0.016/0.017
1.7/1.7 4.1/4.9
0.040/0.035 12.5/6.5
DI =Digit 1; D2-Digit 2; WR=Wrist; MP=Midpalm.
Table 2--Nerve conduction studies with inching (pre-operative/postoperative)
Median sensory--Digit 1 Point A B C D E Median mixed--Midpalm Point A B C D E F Median motor--Thenar Point A B C D E
Latency (msec)
Amplitude
3.5/3.5 3.2/3.1 2.8/2.7 2.6/2.3 2.3/*
0.007/0.010 0.007/0.010 0.0012/0.011 0.0012/0.013 0.0011/*
3.5/3.7 3.8/4.1 4.4/4.6 4.7/5.0 4.9/5.5 5.1/* .
0.043/0.052 0.040/0.043 0.023/0.034 0.021/0.025 0.018/0.022 0.018/*
4.9/4.5 4.6/4.1 3.3/3.4 2.9/3.1 */2.5
6.8/6.5 6.7/6.6 7.1/6.6 7.0/6.5 */5.6
(my)
*Not performed.
Fig 1
tion studies using a modified inching technique (Kimura, 1979; Fig 2). Three parameters were used. First, median SNAPs were recorded at the thumb while stimulating antidromically proximal to the wrist (point A). The cathode was then moved distally in increments of 2 cm and the latencies recorded. Secondly, the median nerve mixed fibres were stimulated distally at the same points
Appearance of the lesion near the left wrist (arrow). 475
476
THE JOURNAL OF HAND SURGERYVOL. 20B No. 4 AUGUST 1995
and motor fibre stimulation. The evoked amplitudes dropped significantly across the same segment in all three parameters. Needle electromyography revealed reduced recruitment in the abductor pollicis brevis muscle, but normal insertional activity and motor unit action potentials. A magnetic resonance imaging study was obtained using coronal, axial and sagittal images. This confirmed a 2 cm mass with multiple septations intimately related to the median nerve. On the T 1-weighted images, the mass appeared similar in density to muscle, and on T2-weighted images, similar to muscle and fat. An ultrasound study was also done, which confirmed that the mass was largely cystic in view of throughtransmission and lack of internal echoes. Over the next few weeks, the patient noticed an increase in both the size of the lesion and thumb paraesthesiae. During surgery, the median nerve appeared normal except for a 2.5 cm area of cystic enlargement just proximal to the carpal tunnel. Extending from the cystic mass was a stalk which passed below the flexor retinaculum and entered the radiocarpal joint (Fig 4). This was first isolated and transected. It revealed clear synovial fluid (Fig 5) and the point of entry into the radio-carpal joint was excised. Using an operating microscope, interfascicular dissection was begun in the nerve proximal to the mass, proceeding into it, and carefully separating the fascicles. Several of these were extremely attenuated, but were in continuity. As the dissection proceeded, areas of extremely thin fibrous walled cavities filled with gelatinous material were entered. Multiple cavities within the nerve were decompressed. The entire lesion could not
[ D C B A Fig 2
Electrode placement across the median nerve to perform the inching study as explained in the text. The shaded zone represents the area of sensory loss.
while recording the nerve action potentials at the elbow. Thirdly, thenar compound muscle action potentials were recorded after stimulation at points A, B, and C. The results are shown at the top of Figure 3. As can be seen, the latencies showed significant slowing across the B-C segment overlying the lesion mainly after mixed
Pre-op Median Mixed
Pre-op Median Sensory
Pre-op Median Motor
A 8 C
c
~
D
~
~
c
D
D
D
E
~t E F
o~s 1:o
20uV ~_ 1msec
lls
ms
15
0.'5
20 uv / 1rnsec
1.'5
Post-op Median Mixed
Post-op Median Sensory
o:s 11o 1~5
5rnV~ N\A* 2msec
ms
ms
Post-op Median Motor A B
C C
D
__.._.__.,/v----~ °
E
E
F
E
2OuV - N \ A I¢ 1 rnsec
Fig 3
01S
110 ms
lls
20uV -N\A* 1msec
0
015 I~0 £s ms
E
5mY [ _ 2msec
01s
1~o 1;s ms
Results of the inching study before (top traces) and after surgery (bottom traces). The histograms illustrate the latency differences between successive sites. Note the pre-operative reduction in the area and the increase in the latency of the median-evoked responses across the B-C segment overlying the lesion.
477
GANGLION IN MEDIAN NERVE
Fig 4
The median nerve at exploration. The instrument is beneath the stalk of ganglion where it enters the nerve (arrow). Note the cystic appearance.
Fig 5
A droplet of clear gelatinous material (arrow) emerging from the cystic lesion in the nerve. Multiple loculated areas containing similar fluid were noted.
be excised without risk of damaging nerve fascicles and for this reason the area was marsupialized and left open. After the operation, the patient had pain and hypoaesthesia over the palmar aspect of the whole thumb that resolved in 1 week. Post-operative nerve conduction studies showed significant improvement of the conduction block and slowing 4 months after the surgery (Fig 3). There was mild but insignificant prolongation of the total median sensory and mixed latencies across the whole A-E segment (Table 2). DISCUSSION This case illustrates an unusual aetiology of thumb involvement in a median mononeuropathy. The reduced median SNAP amplitude to the thumb and the prolonged median motor distal latency along with a positive Tinel's sign suggested carpal tunnel syndrome. However,
the preservation of a normal median mid-palmar orthodromic response made us question the diagnosis (Kimura, 1979). The modified inching technique demonstrated both significant conduction slowing and amplitude drop across a discrete segment overlying the lesion and was consistent with focal demyelination. A review of the fascicular topography of the median nerve in the distal forearm shows that the thenar muscular branch ~nd the cutaneous fibres from the thumb and lateral palm join together on the radial side of the median nerve in the distal forearm (Sunderland, 1978). Accordingly, a laterally located lesion in the distal forearm may present with isolated involvement of these fibres. In contrast to this case, ganglion cysts at the wrist have selectively affected the palmar cutaneous branch and spared the cutaneous digital fibres (Buckmiller and Richard, 1987; Gessini et al, 1983). Another unusual feature of this case is the aetiology of the compression. Although the cystic appearance and the location of the mass resembled cysts of the flexor tendon sheath (Buckmiller and Richard, 1987), the rapid onset of symptoms and the increase in size suggested an aggressive intraneurat or neoplastic process. The cyst originated from the radio-carpal joint, entered the nerve, expanded proximally, and infiltrated along fascicles, distending particularly the lateral aspect of the median nerve. Intraneural ganglion cysts are uncommon and those involving the median nerve are exceptional. Hartwell (1901) was the first to describe a case, but his patient had a high lesion located medial to the biceps muscle. During surgery in our case, the nerve enlargement contained thick fluid but otherwise appeared normal. Microscopic examination of one nerve fascicle showed Schwann cell and fibroblast proliferation, extensive demyelination and some axonal degeneration. Our electrophysiologic findings and post-operative recovery are also consistent with focal demyelination. A series from France (Allieu and Cenac, 1989) included one patient with a median nerve pseudocyst proximal to the pronator teres arch. Electrophysiological data were not explicit. These authors emphasized the peculiar lack of median nerve pseudocysts near the carpal tunnel. We have not found similar reports in our literature review and wish to add our case to the list of causes of median neuropathy affecting the thumb.
References ALLIEU, Y. and CENAC, P. E. (1989). Peripheral nerve mucoid degeneration of the upper extremity. Journal of Hand Surgery, 14A: 2(1): 189-194. BUCKMILLER, J. F. and RICHARD, T. A. (1987). Isolated compression neuropathy of the palmar cutaneous branch of the median nerve. Journal of Hand Surgery, 12A: 1: 97-99. DAWSON, D. M., HALLETT, M. and MILLENDER, L. H. (1990). Entrapment Neuropathies, 2nd Edn. Boston, Little, Brown, 253-267. GESSINI, L., JANDOLO, B., PIETRANGELI, A. and SENESE, A. (1983). Compression of the palmar cutaneous nerve by ganglions of the wrist. Journal of Neurosurgical Sciences, 27: 241-243.
478 H A R T W E L L , A. S. (1901). Cystic tumor of median nerve: Operation: Restoration of function. Boston Medical and Surgical Journal, 144: 582-583. K I M U R A , J. (1979). The carpal tunnel syndrome: Localization of conduction abnormalities within the distal segment of the median nerve. Brain, 102: 619 635.
T H E J O U R N A L O F H A N D SURGERY VOL. 20B No. 4 A U G U S T 1995 S U N D E R L A N D , S. (1978). Nerves and Nerve Injuries, 2nd Edn, Edinburgh, Churchill Livingstone, 672-677.
Accepted: 9 February 1995 Safwan Jaradeh MD, Department of Neurology, MCW Clinic at Froedtert, 9200 West, Wisconsin Avenue, Milwaukee, Wisconsin 53226, USA. © 1995 The British Society for Surgery of the Hand