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A Man with Burning Sensations in the Thigh
Case 27
A Man with Burning Sensations in the Thigh
A 48-year-old, mildly obese man developed burning paresthesias in the outer aspect of the right thigh of an insidious onset. This increased when he was working. He denied weakness or other neurologic problems. Past medical history was unremarkable. Family history was noncontributory; the patient drank moderately. Examination revealed normal mentation and cranial nerves. Motor examination was normal. Reflexes were normal and equal. There was a patchy area in the right lateral thigh where he had an unusual sensation when touched, and felt somewhat numb when compared with the rest of the leg or the other side. The examination was otherwise unremarkable.
WHAT IS THE DIFFERENTIAL DIAGNOSIS? A lumbar radiculopathy, plexopathy, or femoral neuropathy should be included in the differential diagnosis, but the lack of back pain, weakness, and normal reflexes make these unlikely. The symptoms suggest a lateral femoral cutaneous neuropathy.
WHAT TESTS SHOULD BE ORDERED? A complete metabolic panel, a 2-hour postprandial blood sugar test, and the sedimentation rate were normal.
AN EMG TEST WAS PERFORMED Motor Nerve Studies
F-wave and Tibial H-reflex Studies
Nerve and Site
Latency (ms)
Amplitude (mV)
Conduction Velocity (m/s)
Peroneal Nerve R.
Normal £ 5.7
Normal ≥3
Normal ≥ 40
3.7 10.9
8 8
— 45
Tibial Nerve R.
Normal £ 5.3
Normal ≥4
Normal ≥ 40
Ankle Pop. fossa
4.7 14.3
6 6
— 42
Ankle Fibular head
Nerve Peroneal nerve R. Tibial nerve R. H-reflex R. H-reflex L.
Normal Latency ≥ (ms)
50.2 51.2 33.0 32.8
54 54 34 34
Sensory Nerve Studies
Nerve Sural nerve R. Lat. fem. cut. R. Lat. fem. cut. L.
210
Latency (ms)
Onset Latency (ms)
Normal Onset Latency £ (ms)
Amp (mV)
Normal Amp ≥ (mV)
3.8 NR 3.5
4.0 3.6 3.6
21 NR 10
11 3–10 3–10
211
A Man with Burning Sensations in the Thigh
EMG Data Muscle
Insrt Activity
Fibs
Pos Waves
Fasc
Amp
Dur
Poly
Pattern
Lumbar paraspinal R. Tensor fasciae latae R. Biceps femoris-long head R. Tibialis anterior R. Gastrocnemius R.
Norm Norm Norm Norm Norm
None None None None None
None None None None None
None None None None None
Norm Norm Norm Norm Norm
Norm Norm Norm Norm Norm
None None None None None
Full Full Full Full Full
1 ms
A
400 V
2
5 uV N: 13
A
15 V
3
5 uV N: 17
A
15 V
FIGURE 27-1 An absent lateral femoral cutaneous SNAP in the right side (bottom), but present on the left (top) (10 µV/20 msec).
WHAT WERE THE EMG FINDINGS? This test revealed normal motor and sensory conduction velocities, CMAPs and SNAPs amplitudes. The lateral femoral cutaneous SNAP was not elicited on the right. The opposite side was tested, and a small SNAP was obtained (Fig. 27-1). Needle test of the right leg and paraspinal muscles were normal. In summary, this EMG was normal, except for absent right lateral femoral cutaneous nerve SNAPs. The patient was treated with a local steroid injection in the right lateral femoral cutaneous nerve with marked improvement.
DISCUSSION It was concluded that this patient had neuropathy of the lateral femoral cutaneous nerve, or meralgia paresthetica (from meros: thigh, algos: pain; MP). This condition is also called Roth-Bernhardt syndrome.1 The lateral femoral cutaneous nerve (or lateral cutaneous nerve of the thigh) arises from the dorsal division of the ventral primary rami of L2 and L3 roots. It emerges from the lateral border of the psoas crossing the iliacus muscle, and then passes under the lateral end of the inguinal ligament, through a small tunnel formed by the lateral attachment of the anterior superior iliac spine2; there are many variations of this course.3 The lateral femoral cutaneous nerve could be compressed in several areas, but is often idiopathic. It is frequently seen in diabetics.1,2 The term meralgia paresthetica is used not only for the idiopathic form of the neuropathy, but also for those with compression or diabetes. Other causes include neuromas, hematomas, surgery, pregnancy, obesity, injury, lacerations, surgical injury, and chronic compression by the sartorius muscle and by the tensor fasciae latae.1–7 It is also caused by compression from seat belts, wallets, guns, heavy keys, wearing “hip-hugger” trousers,8 and soldiers wearing body armor.9 In most patients, no cause is identifiable, but likely the nerve is compressed or kinked as it goes through the inguinal ligaments4 (Fig. 27-2). The symptoms consist of burning and a “funny feeling,” accompanied by numbness in the lateral aspect of the thigh, as Sigmund Freud described his own case.10 There could be tenderness to palpation below the anterior superior iliac spine. The diagnosis of MP is usually made clinically and by ruling out predisposing causes. The differential diagnosis includes L2 radiculopathy or plexopathies; MP could also be the initial manifestation of retroperitoneal tumors.11 Electromyographic studies should include measurement of the SNAPs of the lateral femoral cutaneous nerve12,13 and are used to rule out other causes such as radiculopathies or plexopathies. Unfortunately, in our experience and
212
Case 27
SUMMARY This man developed burning paresthesias in the thigh and was diagnosed as having meralgia paresthetica. He was treated with corticosteroid injections with benefit.
IMPORTANT POINTS Lateral cutaneous nerve of the thigh
FIGURE 27-2 Diagram of the lateral femoral cutaneous nerve and its root, a common site of entrapment.
• Meralgia paresthetica is a mononeuropathy of the lateral femoral cutaneous nerve. • The disorder has many causes such as external compression, obesity, pregnancy, compression at the inguinal ligament, at the anterior superior iliac spine, the sartorius and tensor fasciae latae muscles, and neuromas. • The disease is likely benign, but occasionally may be a manifestation of a more severe disease, such as retroperitoneal tumors. • Electrophysiologic studies are useful to rule out other conditions such as radiculopathy. • An absent or low-amplitude SNAP in the affected side compared with the normal side is used for diagnosis, but this could be absent in normal people. Thus one should demonstrate its presence in the normal side first to make a diagnosis. If the SNAPs are absent in both sides, this could be technical; the diagnosis is based mostly on the history, clinical examination, and the absence of other abnormal findings on EMG. • The treatment of meralgia paresthesia consists of removal of the cause of compression; local steroid injections are helpful.
REFERENCES that of others, the lateral femoral cutaneous SNAP is hard to obtain, even in normals and particularly in obese people; for this reason, one should always check the healthy side to make sure this is present. If the SNAP is absent on the healthy side, then likely the absent SNAP in the affected nerve is also caused by technical difficulties, particularly when using surface stimulating and recording techniques.1,13 In a recent report, however, a SNAP was obtained in the normal side in most patients with MP using needle recording electrodes.14 Another study stressed the need to consider variability of the course of the nerve when obtaining the SNAP.15 Somatosensory-evoked responses with needle stimulation can be used in diagnosis.16,17 The prognosis is favorable. Patients respond to conservative management; local injections of corticosteroids and analgesics are of benefit.1 Surgical decompression is sometimes necessary.
1. Dumitru D, Zwarts MJ: Lumbosacral plexopathies and proximal mononeuropathies. In Dumitru D, Amato AA, Zwarts MJ (eds): Electrodiagnostic Medicine, 2nd ed. Philadelphia, Hanley & Belfus, 2002, pp 865–883. 2. Stewart JD: Lateral cutaneous nerve of the thigh. In Stewart JD (ed): Focal Peripheral Neuropathies, 3rd ed. Philadelphia, Lippincott, Williams & Wilkins, 2000, pp 475–481. 3. Boyce JR: Meralgia paresthetica and tight trousers. JAMA 251:1553, 1984. 4. Ecker AD, Woltman HW: Meralgia paresthetica: A report of one hundred and fifty cases. JAMA 110:1650–1652, 1938. 5. Ecker AD: Diagnosis of meralgia paresthetica. JAMA 253(7):976, 1985. 6. Ghent WR: Further studies on meralgia paresthetica. Can Med Assoc J 85:871–875, 1961. 7. Orton D: Meralgia paresthetica from a wallet. JAMA 252(24):3368, 1984. 8. Park JW, Kim DH, Hwang M, Bun HR: Meralgia paresthetica caused by hip huggers in a patient with aberrant
A Man with Burning Sensations in the Thigh
9.
10. 11. 12.
13.
course of the lateral femoral cutaneous nerve. Muscle Nerve 35(5):678–680, 2007. Fargo MV, Konitzer LN: Meralgia paresthetica due to body armor wear in U.S. soldiers serving in Iraq: A case report and review of literature. Mil Med 172(6):663–665, 2007. Schiller F: Sigmund Freud’s meralgia paresthetica. Neurology 35:557–558, 1985. Flowers RS: Meralgia paresthetica: A clue to retroperitoneal malignant tumor. Am J Surg 116:89–92, 1968. Lagueny A, Deliac MM, Deliac P, Durandeau A: Diagnostic and prognostic value of electrophysiologic tests in meralgia paresthetica. Muscle Nerve 14:51–56, 1991. Lysens R, Vandendriessche G, Van Mol Y, Rosselle N: The sensory conduction velocity in the cutaneous femoris lateralis nerve in normal adult subjects and in patients with com-
14.
15.
16.
17.
213
plaints suggesting meralgia paresthetica. Electromyogr Clin Neurophysiol 21:505–510, 1981. Seror P, Seror R: Meralgia paresthetica: Clinical and electrophysiological diagnosis in 120 cases. Muscle and Nerve 33:650–654, 2006. Shin YB, Park JH, Kwon DR, et al: Variability in conduction of the lateral renocutaneous nerve. Muscle Nerve 33:645– 649, 2006. Seror P: Lateral femoral cutaneous nerve conduction v somatosensory evoked potentials for electrodiagnosis of meralgia paresthetica. Am J Phys Med Rehabil 78:313–316, 1992. Po HL, Mei SN: Meralgia paresthetica: The diagnostic value of somatosensory-evoked potentials. Arch Phys Med Rehabil 73:70–72, 1991.
A Man with Burning Sensations in the Thigh
A 48-year-old, mildly obese man developed burning paresthesias in the outer aspect of the right thigh of an insidious onset. This increased when he was working. He denied weakness or other neurologic problems. Past medical history was unremarkable. Family history was noncontributory; the patient drank moderately. Examination revealed normal mentation and cranial nerves. Motor examination was normal. Reflexes were normal and equal. There was a patchy area in the right lateral thigh where he had an unusual sensation when touched, and felt somewhat numb when compared with the rest of the leg or the other side. The examination was otherwise unremarkable.
WHAT IS THE DIFFERENTIAL DIAGNOSIS? A lumbar radiculopathy, plexopathy, or femoral neuropathy should be included in the differential diagnosis, but the lack of back pain, weakness, and normal reflexes make these unlikely. The symptoms suggest a lateral femoral cutaneous neuropathy.
WHAT TESTS SHOULD BE ORDERED? A complete metabolic panel, a 2-hour postprandial blood sugar test, and the sedimentation rate were normal.
AN EMG TEST WAS PERFORMED Motor Nerve Studies
F-wave and Tibial H-reflex Studies
Nerve and Site
Latency (ms)
Amplitude (mV)
Conduction Velocity (m/s)
Peroneal Nerve R.
Normal £ 5.7
Normal ≥3
Normal ≥ 40
3.7 10.9
8 8
— 45
Tibial Nerve R.
Normal £ 5.3
Normal ≥4
Normal ≥ 40
Ankle Pop. fossa
4.7 14.3
6 6
— 42
Ankle Fibular head
Nerve Peroneal nerve R. Tibial nerve R. H-reflex R. H-reflex L.
Normal Latency ≥ (ms)
50.2 51.2 33.0 32.8
54 54 34 34
Sensory Nerve Studies
Nerve Sural nerve R. Lat. fem. cut. R. Lat. fem. cut. L.
210
Latency (ms)
Onset Latency (ms)
Normal Onset Latency £ (ms)
Amp (mV)
Normal Amp ≥ (mV)
3.8 NR 3.5
4.0 3.6 3.6
21 NR 10
11 3–10 3–10
211
A Man with Burning Sensations in the Thigh
EMG Data Muscle
Insrt Activity
Fibs
Pos Waves
Fasc
Amp
Dur
Poly
Pattern
Lumbar paraspinal R. Tensor fasciae latae R. Biceps femoris-long head R. Tibialis anterior R. Gastrocnemius R.
Norm Norm Norm Norm Norm
None None None None None
None None None None None
None None None None None
Norm Norm Norm Norm Norm
Norm Norm Norm Norm Norm
None None None None None
Full Full Full Full Full
1 ms
A
400 V
2
5 uV N: 13
A
15 V
3
5 uV N: 17
A
15 V
FIGURE 27-1 An absent lateral femoral cutaneous SNAP in the right side (bottom), but present on the left (top) (10 µV/20 msec).
WHAT WERE THE EMG FINDINGS? This test revealed normal motor and sensory conduction velocities, CMAPs and SNAPs amplitudes. The lateral femoral cutaneous SNAP was not elicited on the right. The opposite side was tested, and a small SNAP was obtained (Fig. 27-1). Needle test of the right leg and paraspinal muscles were normal. In summary, this EMG was normal, except for absent right lateral femoral cutaneous nerve SNAPs. The patient was treated with a local steroid injection in the right lateral femoral cutaneous nerve with marked improvement.
DISCUSSION It was concluded that this patient had neuropathy of the lateral femoral cutaneous nerve, or meralgia paresthetica (from meros: thigh, algos: pain; MP). This condition is also called Roth-Bernhardt syndrome.1 The lateral femoral cutaneous nerve (or lateral cutaneous nerve of the thigh) arises from the dorsal division of the ventral primary rami of L2 and L3 roots. It emerges from the lateral border of the psoas crossing the iliacus muscle, and then passes under the lateral end of the inguinal ligament, through a small tunnel formed by the lateral attachment of the anterior superior iliac spine2; there are many variations of this course.3 The lateral femoral cutaneous nerve could be compressed in several areas, but is often idiopathic. It is frequently seen in diabetics.1,2 The term meralgia paresthetica is used not only for the idiopathic form of the neuropathy, but also for those with compression or diabetes. Other causes include neuromas, hematomas, surgery, pregnancy, obesity, injury, lacerations, surgical injury, and chronic compression by the sartorius muscle and by the tensor fasciae latae.1–7 It is also caused by compression from seat belts, wallets, guns, heavy keys, wearing “hip-hugger” trousers,8 and soldiers wearing body armor.9 In most patients, no cause is identifiable, but likely the nerve is compressed or kinked as it goes through the inguinal ligaments4 (Fig. 27-2). The symptoms consist of burning and a “funny feeling,” accompanied by numbness in the lateral aspect of the thigh, as Sigmund Freud described his own case.10 There could be tenderness to palpation below the anterior superior iliac spine. The diagnosis of MP is usually made clinically and by ruling out predisposing causes. The differential diagnosis includes L2 radiculopathy or plexopathies; MP could also be the initial manifestation of retroperitoneal tumors.11 Electromyographic studies should include measurement of the SNAPs of the lateral femoral cutaneous nerve12,13 and are used to rule out other causes such as radiculopathies or plexopathies. Unfortunately, in our experience and
212
Case 27
SUMMARY This man developed burning paresthesias in the thigh and was diagnosed as having meralgia paresthetica. He was treated with corticosteroid injections with benefit.
IMPORTANT POINTS Lateral cutaneous nerve of the thigh
FIGURE 27-2 Diagram of the lateral femoral cutaneous nerve and its root, a common site of entrapment.
• Meralgia paresthetica is a mononeuropathy of the lateral femoral cutaneous nerve. • The disorder has many causes such as external compression, obesity, pregnancy, compression at the inguinal ligament, at the anterior superior iliac spine, the sartorius and tensor fasciae latae muscles, and neuromas. • The disease is likely benign, but occasionally may be a manifestation of a more severe disease, such as retroperitoneal tumors. • Electrophysiologic studies are useful to rule out other conditions such as radiculopathy. • An absent or low-amplitude SNAP in the affected side compared with the normal side is used for diagnosis, but this could be absent in normal people. Thus one should demonstrate its presence in the normal side first to make a diagnosis. If the SNAPs are absent in both sides, this could be technical; the diagnosis is based mostly on the history, clinical examination, and the absence of other abnormal findings on EMG. • The treatment of meralgia paresthesia consists of removal of the cause of compression; local steroid injections are helpful.
REFERENCES that of others, the lateral femoral cutaneous SNAP is hard to obtain, even in normals and particularly in obese people; for this reason, one should always check the healthy side to make sure this is present. If the SNAP is absent on the healthy side, then likely the absent SNAP in the affected nerve is also caused by technical difficulties, particularly when using surface stimulating and recording techniques.1,13 In a recent report, however, a SNAP was obtained in the normal side in most patients with MP using needle recording electrodes.14 Another study stressed the need to consider variability of the course of the nerve when obtaining the SNAP.15 Somatosensory-evoked responses with needle stimulation can be used in diagnosis.16,17 The prognosis is favorable. Patients respond to conservative management; local injections of corticosteroids and analgesics are of benefit.1 Surgical decompression is sometimes necessary.
1. Dumitru D, Zwarts MJ: Lumbosacral plexopathies and proximal mononeuropathies. In Dumitru D, Amato AA, Zwarts MJ (eds): Electrodiagnostic Medicine, 2nd ed. Philadelphia, Hanley & Belfus, 2002, pp 865–883. 2. Stewart JD: Lateral cutaneous nerve of the thigh. In Stewart JD (ed): Focal Peripheral Neuropathies, 3rd ed. Philadelphia, Lippincott, Williams & Wilkins, 2000, pp 475–481. 3. Boyce JR: Meralgia paresthetica and tight trousers. JAMA 251:1553, 1984. 4. Ecker AD, Woltman HW: Meralgia paresthetica: A report of one hundred and fifty cases. JAMA 110:1650–1652, 1938. 5. Ecker AD: Diagnosis of meralgia paresthetica. JAMA 253(7):976, 1985. 6. Ghent WR: Further studies on meralgia paresthetica. Can Med Assoc J 85:871–875, 1961. 7. Orton D: Meralgia paresthetica from a wallet. JAMA 252(24):3368, 1984. 8. Park JW, Kim DH, Hwang M, Bun HR: Meralgia paresthetica caused by hip huggers in a patient with aberrant
A Man with Burning Sensations in the Thigh
9.
10. 11. 12.
13.
course of the lateral femoral cutaneous nerve. Muscle Nerve 35(5):678–680, 2007. Fargo MV, Konitzer LN: Meralgia paresthetica due to body armor wear in U.S. soldiers serving in Iraq: A case report and review of literature. Mil Med 172(6):663–665, 2007. Schiller F: Sigmund Freud’s meralgia paresthetica. Neurology 35:557–558, 1985. Flowers RS: Meralgia paresthetica: A clue to retroperitoneal malignant tumor. Am J Surg 116:89–92, 1968. Lagueny A, Deliac MM, Deliac P, Durandeau A: Diagnostic and prognostic value of electrophysiologic tests in meralgia paresthetica. Muscle Nerve 14:51–56, 1991. Lysens R, Vandendriessche G, Van Mol Y, Rosselle N: The sensory conduction velocity in the cutaneous femoris lateralis nerve in normal adult subjects and in patients with com-
14.
15.
16.
17.
213
plaints suggesting meralgia paresthetica. Electromyogr Clin Neurophysiol 21:505–510, 1981. Seror P, Seror R: Meralgia paresthetica: Clinical and electrophysiological diagnosis in 120 cases. Muscle and Nerve 33:650–654, 2006. Shin YB, Park JH, Kwon DR, et al: Variability in conduction of the lateral renocutaneous nerve. Muscle Nerve 33:645– 649, 2006. Seror P: Lateral femoral cutaneous nerve conduction v somatosensory evoked potentials for electrodiagnosis of meralgia paresthetica. Am J Phys Med Rehabil 78:313–316, 1992. Po HL, Mei SN: Meralgia paresthetica: The diagnostic value of somatosensory-evoked potentials. Arch Phys Med Rehabil 73:70–72, 1991.