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Demyelinating focal motor neuropathy of the ulnar nerve masquerading as compression in Guyon's canal: A case report
Demyelinating Focal Motor Neuropathy of the Ulnar Nerve Masquerading as Compression in Guyon’s Canal: A Case Report Manjit S. Dhillon, MD, Mary Lynn Chu, MD, Martin A. Posner, MD, New York, NY Ulnar nerve–innervated intrinsic muscle weakness, in the absence of sensory complaints or deficits, usually is the result of compression at the ulnar nerve in zone II of Guyon’s canal. In rare instances the problem is not caused by a compressive neuropathy but by a demyelinating focal motor neuropathy. Demyelinating neuropathies have been well documented in the neurologic literature but they have received little attention in the hand surgery literature. We report on one such case and the importance of differentiating the 2 neuropathies. Although surgery often is necessary for a compressive neuropathy it is contraindicated for a demyelinating neuropathy. (J Hand Surg 2003;28A:48-51. Copyright © 2003 by the American Society for Surgery of the Hand.) Key words: Ulnar nerve, demyelinating neuropathy, focal motor neuropathy.
Weakness of the ulnar nerve–innervated intrinsic muscles of the hand, in the absence of sensory complaints or deficits, usually is caused by compression of the ulnar nerve in zone II of Guyon’s canal. Occasionally the problem may not be the result of a compressive neuropathy but rather a demyelinating neuropathy. It is important to differentiate between the 2 because treatment for each is different. For the chronic nerve compression with muscle weakness surgery is necessary, whereas such treatment for a demyelinating neuropathy is contraindicated. Demyelinating neuropathies have been well documented in the neurologic literature but have received scant attention in the orthopedic and hand literature.1–10 We present a case of a demyelinating neuropathy that presented with weakness confined to ulnar nerve–innervated intrinsic musFrom the Hand and Neurology Services, New York University–Hospital for Joint Diseases Department of Orthopaedic Surgery, New York, NY. Received for publication September 4, 2001; accepted in revised form August 28, 2002. No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. Reprint requests: Martin A. Posner, MD, Surgery of the Hand, 2 East 88th St., New York, NY 10128. Copyright © 2003 by the American Society for Surgery of the Hand 0363-5023/03/28A01-0008$35.00/0 doi:10.1053/jhsu.2003.50015
THE JOURNAL OF HAND SURGERY
48
cles in the hand. It initially was misdiagnosed as a compressive neuropathy of the motor division of the ulnar nerve.
Case Report A 30-year-old woman presented with a 4- to 5-month history of progressive weakness of her left hand. She had no sensory complaints and was completely pain free. Her past medical history and family history were noncontributory. On physical examination there was severe weakness and wasting of the ulnar nerve–innervated intrinsic muscles in the left hand with clawing of the ring and small fingers. There was no weakness of the intrinsic muscles innervated by the median nerve or weakness of the muscles in the forearm and arm. Sensibility was intact including 2-point discrimination. There was no tenderness or palpable mass anywhere along the course of the ulnar nerve from the upper arm to the hand and there were no Tinel’s signs with percussion over the nerve in the elbow area or at the wrist. The remainder of the neurologic examination was normal except for an absent right-ankle jerk. Radiographs of the left elbow, wrist, and hand were negative. Electrodiagnostic studies had been done at another institution and were interpreted as showing ulnar nerve
49 Dhillon, Chu, and Posner / Motor Neuropathy of the Ulnar Nerve
compression but the site of compression was not determined. The physician who ordered those studies had recommended decompression of the ulnar nerve in the canal of Guyon. The absence of a mass and, more importantly, the absence of any sensitivity with percussion over the ulnar nerve in the wrist or palm, however, were causes for concern that the problem was not caused by a compressive neuropathy. New electrodiagnostic studies were obtained and the positive findings were confined to the left ulnar nerve. Conduction of the motor fascicles showed normal latencies and conduction velocities but there was a marked drop in amplitude distal to the elbow. By using the inching stimulation technique the site was localized at 12 cm proximal to the pisiform bone. Stimulation of the sensory fascicles also showed normal latencies and conduction velocities and as with the motor fascicles a similar drop in amplitude 12 cm proximal to the pisiform. Conduction in the dorsal sensory branch of the nerve could not be recorded and F-wave latencies were normal. Electromyography showed acute denervation of the interossei muscles and abductor digiti minimi. The electrodiagnostic studies were consistent with a focal motor neuropathy of the ulnar nerve. Magnetic resonance imaging of the forearm was done to rule out an intraneural tumor or a soft-tissue mass adjacent to the ulnar nerve. The study was negative. Over the next 2 months the patient reported an improvement in grip strength and she noted a progressive decrease in clawing. When examined 2 months later there was no clawing and intrinsic muscle strength was normal. A spinal tap that had been considered earlier was therefore not performed. The patient remained symptom free for the next 9 months. During the sixth month of her first pregnancy, however, she again noted weakness in her left hand. As with the initial episode she had no sensory complaints and no pain. The physical examination was almost identical to the first examination except weakness of the ulnar nerve–innervated intrinsic muscles was less severe and there was only slight clawing confined to the small finger. Sensibility was intact and there was no tenderness or Tinel’s sign anywhere along the course of the ulnar nerve. Muscle weakness continued to worsen as the pregnancy progressed but it began to improve soon after delivery. It returned to normal 4 weeks postpartum. The patient has remained asymp-
tomatic for more than 1 year and she has had no recurrence of muscle weakness.
Discussion Demyelinating neuropathies comprise a large group of inflammatory nerve disorders that present either as an acute inflammatory demyelinating polyneuropathy or a chronic inflammatory demyelinating polyneuropathy (CIDP). Pathogenetically both neuropathies may be variants of the same disorder but with major differences, primarily in their temporal evolution. Acute inflammatory demyelinating polyneuropathy, more commonly referred to as Guillain-Barre´ syndrome, is frequently preceded by a viral upper-respiratory infection. It is characterized by an acute onset of motor paralysis associated with mild sensory disturbances and rapid progression to a maximum deficit within days or a few weeks. The condition usually improves over the next several months. Fatalities are extremely rare and are usually caused by infection or autonomic dysfunction.1 Although CIDP also can begin acutely it is more likely to develop slowly and evolve over a period of time varying from many weeks to years. The pattern of clinical progression also is variable.2 It can progress in a steady fashion with relapses and remissions (partial or complete) or it progresses in a stepwise fashion over months or years with fluctuations in the severity of neurologic disability. Chronic inflammatory demyelinating polyneuropathy persists for years and recovery rarely is complete. The etiology of CIDP is unknown but it is thought to be secondary to an acquired autoimmune disease of the myelin in peripheral nerves.2 The condition is characterized by widespread and symmetric muscle weakness and sensory deficits usually affecting the lower limbs. Generally the muscle weakness affects both proximal and distal portions of the limbs. Occasionally trunk muscles and those muscles innervated by the cranial nerves are affected. Chronic inflammatory demyelinating polyneuropathy sometimes is associated with systemic diseases such as lymphomas and lupus erythematosis.3 In 1982 Lewis et al4 reported on a chronic demyelinating neuropathy in a group of patients who predominantly had motor symptoms and electrophysiologic evidence of a multifocal motor conduction block. The condition was later referred to as multifocal motor neuropathy (MMN).4,5 It remains unclear if MMN is a distinct disorder of peripheral nerve myelin
50 The Journal of Hand Surgery / Vol. 28A No. 1 January 2003
Table 1. Compressive Neuropathy vs Demyelinating Neuropathy: Diagnosis and Treatment Demyelinating Neuropathy Compressive Neuropathy Symptoms Pain Distribution Upper ⬎ lower limbs Sensory symptoms Widespread areflexia Physical findings Tinel sign Laboratory findings Cerebrospinal fluid protein ⬎ 100 mg/dL Antiganglioside 1 antibodies Typical electrodiagnostic features
Course of disease Progressive Relapsing Treatment Surgery Intravenous gamma globulin Plasmapheresis Corticosteroid
MMN
CIDP
Variable Anatomy of nerve compressed Yes Yes No
No Asymmetric Yes Rare No
Rare Symmetric No Yes Yes
Yes
No
No
No No
No 30% to 50%
Yes Rare
Focal slowing of nerve conduction across site of compression
Motor conduction block at site(s) unusual for compression
Symmetric features of demyelination
Yes No
Yes Rare
Yes Yes
Frequent No No No
No Yes No No
No Yes Yes Yes
or simply a predominantly motor variant of CIDP.6,7 Clinically CIDP usually presents with symmetric weakness of the lower extremities accompanied by pain and sensory deficits, whereas MMN tends to be asymmetric, more frequently affecting upper limbs than lower limbs and with far fewer sensory complaints. MMN also more commonly affects the intrinsic hand muscles. In both conditions deep tendon reflexes may be reduced or even absent in normal muscles owing to involvement of group Ia afferent sensory fibers from muscle spindles.8 There are differences in laboratory studies between the 2 conditions. Unlike CIDP serum protein electrophoresis and cerebrospinal fluid protein are normal in MMN. Many patients with MMN, however, have high titers of antiganglioside antibodies, particularly antiganglioside 1.9 Adding to the confusion is the name of the disorder. MMN is not necessarily multifocal and it is not always a pure motor neuropathy. Sensory symptoms and deficits have been described and there are cases in which weakness was confined to a single limb, usually an upper limb. This was the clinical presentation in our patient. When only a single nerve is affected the condition is usually referred to as a focal motor neuropathy. Focal neuropathies often progress to MMN and even to CIDP, and the rate of that progression is
variable. Cases have been documented in which progression was delayed for more than 20 years.2 The role of electrodiagnostic studies is critically important because they distinguish between compressive neuropathies that primarily affect motor and/or sensory axons and demyelinating neuropathies that primarily affect myelin sheaths. In compressive neuropathies that are mild and not long standing, nerve conduction studies and distal latencies usually are normal. Evoked potentials also are normal or they may be decreased in size. Slowing of nerve conduction occurs late in a compressive neuropathy and is evidence of focal demyelination at that site. Fibrillation potentials and positive sharp waves on electromyography indicate that axonal degeneration has occurred. Electrodiagnostic studies therefore vary in compressive neuropathies; they are not always diagnostic and false-negative results occur. Electrodiagnostic studies are more consistent in demyelinating neuropathies and are essential in defining a condition that affects the myelin sheath. The key electrodiagnostic component of multifocal motor neuropathy is a conduction block in one or more nerves at a site or sites not normally prone to compression.8 The conduction block most commonly occurs in the forearm, which was the situation in our patient.6,10 Nerve
51 Dhillon, Chu, and Posner / Motor Neuropathy of the Ulnar Nerve
conduction is slowed with prolonged distal and Fwave latencies, and compound action potential amplitude may be normal or there may be dispersion without conduction block. Although electrodiagnostic findings define the disease process, controversies exist. Some maintain that the diagnosis of MMN should be reserved for those cases in which only motor fascicles are affected and that when both motor and sensory fascicles are affected at the same site the disorder should be termed CIDP with multifocal conduction block.3 This terminology only adds to the clinical confusion because MMN often begins with a mononeuropathy that is uncharacteristic of CIDP. Although sensory conduction usually is normal in MMN, low-amplitude responses can be seen, as in our patient. It has been suggested that the sensory axons are not themselves demyelinated, but are injured as an innocent bystander to demyelination of adjacent motor axons.6 Treatment of demyelinating neuropathies has included high-dose intravenous corticosteroids, plasmapheresis, and high-dose intravenous immunoglobulin therapy. The first 2 are mainstays in the treatment of CIDP but there is no consensus for the treatment of MMN because there is insufficient experience. Although corticosteroids alone do not appear to be effective some patients have responded to immunosuppression combined with cyclophosphamide (Table 1).9 Because MMN is a disease of young adults that generally runs an indolent course of years’ duration we anticipate that the condition of our patient eventually will deteriorate and that she will require treatment. The clinical presentation of her condition shows the importance of establishing an accurate diagnosis before recommending surgery for what may appear to be a compressive neuropathy. The absence of tenderness
or a Tinel sign over the presumed site of a nerve compression should alert the physician that that diagnosis may be incorrect. Electrodiagnostic studies usually are helpful in these situations particularly when the clinical findings are questionable. In our patient those studies determined conclusively that the problem was a focal motor demyelinating neuropathy for which surgery was contraindicated.
References 1. Lange DJ, Latov N, Trojaborg W. Acquired neuropathies. In Rowland LP, ed. Merritt’s textbook of neurology. 9th ed. Baltimore: Williams & Wilkins, 1995:657– 660. 2. Verma A, Tandan R, Adesina AM, Pendlebury WW, Fries TJ, Bradley WG. Focal neuropathy preceding chronic inflammatory demyelinating polyradiculoneuropathy by several years. Acta Neurol Scand 1990;81:516 –521. 3. Adams RD, Victor M, Ropper AH. Principles of Neurology. 6th ed. New York: McGraw-Hill, 1997:1337–1338. 4. Lewis RA, Sumner AJ, Brown MJ, Asbury AK. Multifocal demyelinating neuropathy with persistent conduction block. Neurology 1982;32:958 –964. 5. Parry GJ, Clarke S. Multifocal acquired demyelinating neuropathy masquerading as motor neuron disease. Muscle Nerve 1988;11:103–107. 6. Parry GJ. AAEM case report #30: multifocal motor neuropathy. Muscle Nerve 1996;19:269 –276. 7. Parry GJ. Motor neuropathy with multifocal conduction block. In: Griffin JW, Low PA, Poduslo JF, eds. Peripheral neuropathy. Vol. 2. Philadelphia: WB Saunders, 1993: 1518 –1524. 8. Chaudhry V, Corse AM, Cornblath DR, Kuncl RW, Freimer ML, Griffin JW. Multifocal motor neuropathy: electrodiagnostic features. Muscle Nerve 1994;17:198 –205. 9. Asbury AK, Bird SJ. Disorders of peripheral nerve. In: Asbury AK, McKhann GM, McDonald WI, eds. Diseases of the nervous system. Clinical neurobiology. Vol. 1. Philadelphia: WB Saunders, 1992:252–269. 10. Briani C, Brannagan TH III, Trojaborg W, Latov N. Chronic inflammatory demyelinating polyneuropathy. Neuromusc Disord 1996;6:311–325.
Weakness of the ulnar nerve–innervated intrinsic muscles of the hand, in the absence of sensory complaints or deficits, usually is caused by compression of the ulnar nerve in zone II of Guyon’s canal. Occasionally the problem may not be the result of a compressive neuropathy but rather a demyelinating neuropathy. It is important to differentiate between the 2 because treatment for each is different. For the chronic nerve compression with muscle weakness surgery is necessary, whereas such treatment for a demyelinating neuropathy is contraindicated. Demyelinating neuropathies have been well documented in the neurologic literature but have received scant attention in the orthopedic and hand literature.1–10 We present a case of a demyelinating neuropathy that presented with weakness confined to ulnar nerve–innervated intrinsic musFrom the Hand and Neurology Services, New York University–Hospital for Joint Diseases Department of Orthopaedic Surgery, New York, NY. Received for publication September 4, 2001; accepted in revised form August 28, 2002. No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. Reprint requests: Martin A. Posner, MD, Surgery of the Hand, 2 East 88th St., New York, NY 10128. Copyright © 2003 by the American Society for Surgery of the Hand 0363-5023/03/28A01-0008$35.00/0 doi:10.1053/jhsu.2003.50015
THE JOURNAL OF HAND SURGERY
48
cles in the hand. It initially was misdiagnosed as a compressive neuropathy of the motor division of the ulnar nerve.
Case Report A 30-year-old woman presented with a 4- to 5-month history of progressive weakness of her left hand. She had no sensory complaints and was completely pain free. Her past medical history and family history were noncontributory. On physical examination there was severe weakness and wasting of the ulnar nerve–innervated intrinsic muscles in the left hand with clawing of the ring and small fingers. There was no weakness of the intrinsic muscles innervated by the median nerve or weakness of the muscles in the forearm and arm. Sensibility was intact including 2-point discrimination. There was no tenderness or palpable mass anywhere along the course of the ulnar nerve from the upper arm to the hand and there were no Tinel’s signs with percussion over the nerve in the elbow area or at the wrist. The remainder of the neurologic examination was normal except for an absent right-ankle jerk. Radiographs of the left elbow, wrist, and hand were negative. Electrodiagnostic studies had been done at another institution and were interpreted as showing ulnar nerve
49 Dhillon, Chu, and Posner / Motor Neuropathy of the Ulnar Nerve
compression but the site of compression was not determined. The physician who ordered those studies had recommended decompression of the ulnar nerve in the canal of Guyon. The absence of a mass and, more importantly, the absence of any sensitivity with percussion over the ulnar nerve in the wrist or palm, however, were causes for concern that the problem was not caused by a compressive neuropathy. New electrodiagnostic studies were obtained and the positive findings were confined to the left ulnar nerve. Conduction of the motor fascicles showed normal latencies and conduction velocities but there was a marked drop in amplitude distal to the elbow. By using the inching stimulation technique the site was localized at 12 cm proximal to the pisiform bone. Stimulation of the sensory fascicles also showed normal latencies and conduction velocities and as with the motor fascicles a similar drop in amplitude 12 cm proximal to the pisiform. Conduction in the dorsal sensory branch of the nerve could not be recorded and F-wave latencies were normal. Electromyography showed acute denervation of the interossei muscles and abductor digiti minimi. The electrodiagnostic studies were consistent with a focal motor neuropathy of the ulnar nerve. Magnetic resonance imaging of the forearm was done to rule out an intraneural tumor or a soft-tissue mass adjacent to the ulnar nerve. The study was negative. Over the next 2 months the patient reported an improvement in grip strength and she noted a progressive decrease in clawing. When examined 2 months later there was no clawing and intrinsic muscle strength was normal. A spinal tap that had been considered earlier was therefore not performed. The patient remained symptom free for the next 9 months. During the sixth month of her first pregnancy, however, she again noted weakness in her left hand. As with the initial episode she had no sensory complaints and no pain. The physical examination was almost identical to the first examination except weakness of the ulnar nerve–innervated intrinsic muscles was less severe and there was only slight clawing confined to the small finger. Sensibility was intact and there was no tenderness or Tinel’s sign anywhere along the course of the ulnar nerve. Muscle weakness continued to worsen as the pregnancy progressed but it began to improve soon after delivery. It returned to normal 4 weeks postpartum. The patient has remained asymp-
tomatic for more than 1 year and she has had no recurrence of muscle weakness.
Discussion Demyelinating neuropathies comprise a large group of inflammatory nerve disorders that present either as an acute inflammatory demyelinating polyneuropathy or a chronic inflammatory demyelinating polyneuropathy (CIDP). Pathogenetically both neuropathies may be variants of the same disorder but with major differences, primarily in their temporal evolution. Acute inflammatory demyelinating polyneuropathy, more commonly referred to as Guillain-Barre´ syndrome, is frequently preceded by a viral upper-respiratory infection. It is characterized by an acute onset of motor paralysis associated with mild sensory disturbances and rapid progression to a maximum deficit within days or a few weeks. The condition usually improves over the next several months. Fatalities are extremely rare and are usually caused by infection or autonomic dysfunction.1 Although CIDP also can begin acutely it is more likely to develop slowly and evolve over a period of time varying from many weeks to years. The pattern of clinical progression also is variable.2 It can progress in a steady fashion with relapses and remissions (partial or complete) or it progresses in a stepwise fashion over months or years with fluctuations in the severity of neurologic disability. Chronic inflammatory demyelinating polyneuropathy persists for years and recovery rarely is complete. The etiology of CIDP is unknown but it is thought to be secondary to an acquired autoimmune disease of the myelin in peripheral nerves.2 The condition is characterized by widespread and symmetric muscle weakness and sensory deficits usually affecting the lower limbs. Generally the muscle weakness affects both proximal and distal portions of the limbs. Occasionally trunk muscles and those muscles innervated by the cranial nerves are affected. Chronic inflammatory demyelinating polyneuropathy sometimes is associated with systemic diseases such as lymphomas and lupus erythematosis.3 In 1982 Lewis et al4 reported on a chronic demyelinating neuropathy in a group of patients who predominantly had motor symptoms and electrophysiologic evidence of a multifocal motor conduction block. The condition was later referred to as multifocal motor neuropathy (MMN).4,5 It remains unclear if MMN is a distinct disorder of peripheral nerve myelin
50 The Journal of Hand Surgery / Vol. 28A No. 1 January 2003
Table 1. Compressive Neuropathy vs Demyelinating Neuropathy: Diagnosis and Treatment Demyelinating Neuropathy Compressive Neuropathy Symptoms Pain Distribution Upper ⬎ lower limbs Sensory symptoms Widespread areflexia Physical findings Tinel sign Laboratory findings Cerebrospinal fluid protein ⬎ 100 mg/dL Antiganglioside 1 antibodies Typical electrodiagnostic features
Course of disease Progressive Relapsing Treatment Surgery Intravenous gamma globulin Plasmapheresis Corticosteroid
MMN
CIDP
Variable Anatomy of nerve compressed Yes Yes No
No Asymmetric Yes Rare No
Rare Symmetric No Yes Yes
Yes
No
No
No No
No 30% to 50%
Yes Rare
Focal slowing of nerve conduction across site of compression
Motor conduction block at site(s) unusual for compression
Symmetric features of demyelination
Yes No
Yes Rare
Yes Yes
Frequent No No No
No Yes No No
No Yes Yes Yes
or simply a predominantly motor variant of CIDP.6,7 Clinically CIDP usually presents with symmetric weakness of the lower extremities accompanied by pain and sensory deficits, whereas MMN tends to be asymmetric, more frequently affecting upper limbs than lower limbs and with far fewer sensory complaints. MMN also more commonly affects the intrinsic hand muscles. In both conditions deep tendon reflexes may be reduced or even absent in normal muscles owing to involvement of group Ia afferent sensory fibers from muscle spindles.8 There are differences in laboratory studies between the 2 conditions. Unlike CIDP serum protein electrophoresis and cerebrospinal fluid protein are normal in MMN. Many patients with MMN, however, have high titers of antiganglioside antibodies, particularly antiganglioside 1.9 Adding to the confusion is the name of the disorder. MMN is not necessarily multifocal and it is not always a pure motor neuropathy. Sensory symptoms and deficits have been described and there are cases in which weakness was confined to a single limb, usually an upper limb. This was the clinical presentation in our patient. When only a single nerve is affected the condition is usually referred to as a focal motor neuropathy. Focal neuropathies often progress to MMN and even to CIDP, and the rate of that progression is
variable. Cases have been documented in which progression was delayed for more than 20 years.2 The role of electrodiagnostic studies is critically important because they distinguish between compressive neuropathies that primarily affect motor and/or sensory axons and demyelinating neuropathies that primarily affect myelin sheaths. In compressive neuropathies that are mild and not long standing, nerve conduction studies and distal latencies usually are normal. Evoked potentials also are normal or they may be decreased in size. Slowing of nerve conduction occurs late in a compressive neuropathy and is evidence of focal demyelination at that site. Fibrillation potentials and positive sharp waves on electromyography indicate that axonal degeneration has occurred. Electrodiagnostic studies therefore vary in compressive neuropathies; they are not always diagnostic and false-negative results occur. Electrodiagnostic studies are more consistent in demyelinating neuropathies and are essential in defining a condition that affects the myelin sheath. The key electrodiagnostic component of multifocal motor neuropathy is a conduction block in one or more nerves at a site or sites not normally prone to compression.8 The conduction block most commonly occurs in the forearm, which was the situation in our patient.6,10 Nerve
51 Dhillon, Chu, and Posner / Motor Neuropathy of the Ulnar Nerve
conduction is slowed with prolonged distal and Fwave latencies, and compound action potential amplitude may be normal or there may be dispersion without conduction block. Although electrodiagnostic findings define the disease process, controversies exist. Some maintain that the diagnosis of MMN should be reserved for those cases in which only motor fascicles are affected and that when both motor and sensory fascicles are affected at the same site the disorder should be termed CIDP with multifocal conduction block.3 This terminology only adds to the clinical confusion because MMN often begins with a mononeuropathy that is uncharacteristic of CIDP. Although sensory conduction usually is normal in MMN, low-amplitude responses can be seen, as in our patient. It has been suggested that the sensory axons are not themselves demyelinated, but are injured as an innocent bystander to demyelination of adjacent motor axons.6 Treatment of demyelinating neuropathies has included high-dose intravenous corticosteroids, plasmapheresis, and high-dose intravenous immunoglobulin therapy. The first 2 are mainstays in the treatment of CIDP but there is no consensus for the treatment of MMN because there is insufficient experience. Although corticosteroids alone do not appear to be effective some patients have responded to immunosuppression combined with cyclophosphamide (Table 1).9 Because MMN is a disease of young adults that generally runs an indolent course of years’ duration we anticipate that the condition of our patient eventually will deteriorate and that she will require treatment. The clinical presentation of her condition shows the importance of establishing an accurate diagnosis before recommending surgery for what may appear to be a compressive neuropathy. The absence of tenderness
or a Tinel sign over the presumed site of a nerve compression should alert the physician that that diagnosis may be incorrect. Electrodiagnostic studies usually are helpful in these situations particularly when the clinical findings are questionable. In our patient those studies determined conclusively that the problem was a focal motor demyelinating neuropathy for which surgery was contraindicated.
References 1. Lange DJ, Latov N, Trojaborg W. Acquired neuropathies. In Rowland LP, ed. Merritt’s textbook of neurology. 9th ed. Baltimore: Williams & Wilkins, 1995:657– 660. 2. Verma A, Tandan R, Adesina AM, Pendlebury WW, Fries TJ, Bradley WG. Focal neuropathy preceding chronic inflammatory demyelinating polyradiculoneuropathy by several years. Acta Neurol Scand 1990;81:516 –521. 3. Adams RD, Victor M, Ropper AH. Principles of Neurology. 6th ed. New York: McGraw-Hill, 1997:1337–1338. 4. Lewis RA, Sumner AJ, Brown MJ, Asbury AK. Multifocal demyelinating neuropathy with persistent conduction block. Neurology 1982;32:958 –964. 5. Parry GJ, Clarke S. Multifocal acquired demyelinating neuropathy masquerading as motor neuron disease. Muscle Nerve 1988;11:103–107. 6. Parry GJ. AAEM case report #30: multifocal motor neuropathy. Muscle Nerve 1996;19:269 –276. 7. Parry GJ. Motor neuropathy with multifocal conduction block. In: Griffin JW, Low PA, Poduslo JF, eds. Peripheral neuropathy. Vol. 2. Philadelphia: WB Saunders, 1993: 1518 –1524. 8. Chaudhry V, Corse AM, Cornblath DR, Kuncl RW, Freimer ML, Griffin JW. Multifocal motor neuropathy: electrodiagnostic features. Muscle Nerve 1994;17:198 –205. 9. Asbury AK, Bird SJ. Disorders of peripheral nerve. In: Asbury AK, McKhann GM, McDonald WI, eds. Diseases of the nervous system. Clinical neurobiology. Vol. 1. Philadelphia: WB Saunders, 1992:252–269. 10. Briani C, Brannagan TH III, Trojaborg W, Latov N. Chronic inflammatory demyelinating polyneuropathy. Neuromusc Disord 1996;6:311–325.