J Neurosurg 75:652-654, 1991
Sciatic nerve entrapment in a child Case report NAGAGOPAL VENNA, M.D., M.R.C.P., M.R.C.P.(I), MARTIN BIELAWSKI, M.D., AND EDWARD M. SPA'FZ, M.D.
Neurological Unit, Boston Cit)~Hospital and Department of Neurosurgery. University Hospital, Boston University School of Medicine, Boston, Massachusetts v, A child was brought for evaluation of signs of unilateral chronic progressive sciatic nerve dysfunction found to be due to nerve entrapment in the thigh by a fibrovascularband. Sectioningof the band was followed by marked improvement in the nerve function. Compression by a band is a rare but treatable cause of sciatic neuropathy. KEY WORDS
9
sciatic nerve
9
ESIONSof the sciatic nerve trunk are rare. Most are acute, resulting from stab wounds, improperly placed intramuscular injections, or as complications of hip surgery or anticoagulant therapy? Chronic lesions of the sciatic nerve are distinctly unusual and are likely to be misdiagnosed as lesions of the nerve root or lumbosacral plexus. Moreover, if foot deformity ensues from a sciatic nerve lesion in a child, then a developmental orthopedic anomaly or developmental abnormality of the spinal cord or of the cauda equina, such as meningomyelocele or diastematomyelia, is likely to be considered rather than a peripheral nerve-trunk lesion. We describe the case of a child with sciatic nerve entrapment by a fibrovascular band in the thigh to highlight its clinical and neurophysiological features and to stress the improvement of nerve function by surgery.
L
C a s e Report
This 12-year-old boy was referred for evaluation of deformity and weakness of the right foot. The earliest indication appeared 3 years previously, when it was observed that he could not run well. Two years later, his mother noted a tendency of the right foot to turn inward while he walked, which progressed to persistent deformity and wasting of the foot. The boy complained of intermittent tingling down the posterior aspect of the right thigh and calf to the heel but denied pain. The left lower extremity and bladder and bowel control were 652
nerve entrapment
9
fibrovascular band
not affected. There was no history of recent or remote trauma to the back or to the lower extremity. Examination. The boy was healthy-looking and muscular. Abnormalities were confined to the right lower extremity: there was an equinovarus deformity of the right foot. The extensor digitorum brevis muscle, medial plantar foot intrinsic muscles, and (to a lesser extent) the calf and lower parts of the hamstring muscles were atrophied but the gluteal muscles were of normal bulk. Dorsiflexion and eversion of foot and dorsiflexion of the toes were weak, while plantar flexion and inversion of the foot were normal. Knee flexion was slightly weak. Extension of the knee and all movements at the hip were normal. Sensory examination showed blunted pinprick sensation over the lateral border of the foot. The right ankle reflex was absent. The appearance of the skin of the lumbar region and the legs and the shape and mobility of the lumbar spine were normal. No soft-tissue masses or areas of tenderness were detected in the gluteal region or in the thigh, but pressure on the sciatic nerve trunk in the mid-thigh region consistently produced a positive Tinel's sign of paresthesia down the leg. Electromyographic examination of the right lower extremity revealed moderate denervation in the long head of the biceps femoris, medial hamstring, and medial gastrocnemius muscles and mild denervation in the short head of the biceps femoris, tibialis anterior, and peroneus longus muscles (Fig. 1). No abnormalities J. Neurosurg. / Volume 75 / October, 1991
Sciatic nerve entrapment in a child
FIG. 2. Diagram showing the appearances of the sciatic nerve at surgery. The thin arrow points to the proximal end of the nerve and the broad arrow to the fibrovascularband.
FIG. 1. Diagram illustrating the innervation of the gluteal and posterior thigh muscles. The lesion of the sciatic nerve was proximal to the branches to the hamstring muscles. The gluteal muscles, supplied by the superior and inferior gluteal nerves, were spared.
were found in the gluteus maximus, gluteus medius, or the tensor fasciae latae muscles. The patient did not permit examination of the paraspinal muscles. Motor nerve conduction velocity of the posterior tibial nerve was slowed to 28 m/sec, while the motor nerve conduction of the common peroneal nerve was nearly normal. Sural nerve sensory potential, H-reflex, and F-wave responses from the common peroneal and posterior tibial nerves were absent in the right leg. The right sciatic F-wave from the knee to the gastrocnemius soleus muscle was markedly prolonged. The corresponding data from the left leg were normal. Plain radiographs, computerized tomography (CT) scans of the lumbosacral spine and pelvis, a lumbar myelogram, and magnetic resonance images of the gluteal region and thigh were normal. On the basis of the clinical and electrophysiological findings, a lesion of the right sciatic nerve proximal to the origin of the branches to the hamstring muscles in the mid-thigh region was suspected. Operation. Surgery was performed under general endotracheal anesthesia. A long incision was outlined along the projected path of the sciatic nerve over the mid-portion of the posterior aspect of the thigh and was extended superiorly and laterally around the buttock and distally into the popliteal fossa to enable exploration of the nerve in these regions if needed. The J. Neurosurg. / Volume 75/October, 1991
thigh portion of the incision was opened from the gluteal crest to the superior portion of the popliteal fossa. The space between the biceps femoris and the semi-membranosus muscles was developed and the sciatic nerve visualized. The nerve was explored in a proximal to distal direction until the pathology was identified at about the junction of the middle and distal thirds of the thigh. A firm fibrous band was found constricting the sciatic nerve (Fig. 2). The tibial component of the nerve was more severely compressed than the peroneal component. The fibrous band was resected. Inspection and palpation of the nerve revealed no intraneural lesion. Histologically, the band consisted of dense fibrous connective tissue and normal-appearing blood vessels. Postoperative Course. The paresthesias resolved the day after surgery. One month later, there was definite improvement in the strength of dorsiflexion and eversion of the foot and improvement in pinprick sensation over the lateral border of the foot. At l year, strength in all muscle groups of the lower extremity was normal, although the decreased sensation at the foot, absence of the ankle reflex, and the foot deformity persisted. Discussion Localization of the Lesion The clinical and electrophysiologicai evidence suggested a lesion of the sciatic nerve in the mid-thigh region (Fig. 1). There was wasting and weakness of the foot and leg and the hamstring muscles, while the gluteal muscles were unaffected. There was a distinct Tiners sign over the sciatic nerve in the thigh. The absence of sural nerve action potential indicated a lesion distal to the dorsal root ganglion. The absence of denervation in the gluteus maximus, gluteus medius, and the tensor fasciae latae muscles indicated sparing of the inferior and superior gluteal nerves arising directly from the lumbosacral plexus through the roots of L-4, L-5, and S-1 (these nerves accompany the sciatic
653
N. Venna, M. Bielawski, and E. M. Spatz nerve through the greater sciatic notch to the level of the pyriformis muscle). In contrast, the hamstring muscles showed denervation, indicating involvement of the sciatic nerve in the mid-thigh region from where the branches to the hamstring muscles arise. The marked slowing of the motor nerve conduction of the posterior tibial nerve suggested a lesion of the distal nerve trunk rather than of the nerve root or plexus. This also indicated more severe compromise of the tibial component of the sciatic nerve compared to the peroneal component. The sciatic nerve is submerged deeply in the gluteai region and the thigh, and is not accessible for stimulation by surface electrodes. Thus, a conduction delay across a segment of the sciatic nerve cannot be reliably measured as is possible for many superficial nerves of the limbs. Techniques are not yet generally available for the direct measurement of the motor nerve conduction velocity after stimulation of the sciatic nerve through needle electrodes and by recording somatosensory evoked potentials over different parts of the sciatic nerve, over the lumbosacral plexus, and over the spine at the root entry zones:
and relieved by standing; the pain first occurred a few months after he had fallen on his buttocks. Except for Tinel's sign over the sciatic nerve in the thigh, clinical and limited electrophysiological examinations were normal. A myofascial band was discovered at surgery across the sciatic nerve I 0 cm distal to the gluteal fold. Sectioning of the constricting band relieved the symptoms. It was postulated that the band was formed by organization of the posttraumatic hematoma. The present case shows that, if untreated, sciatic nerve compression by a band can progress to severe neurological impairment and deformity. The onset of our patient's symptoms coincided with a growth spurt at the age of 9 years, during which he became distinctly more muscular. The increase in the muscle mass of the thigh and enlargement of the sciatic nerve with growth probably contributed to compromise of the sciatic nerve already entrapped by the band. We believe that awareness of this entity and thorough clinical examination along with focused electrophysiological testing will increase the recognition of this treatable condition. References
Etiology of Sciatic Nerve Palsies Gradually evolving lesions of the sciatic nerve are rare. Extrinsic compression of the nerve has been described in relation to myositis ossificans in the biceps femoris muscle: lipomas, 3 endometriosis) and in the rare syndrome of progressive muscle fibrosis following repeated intramuscular injections of pentazocine.6 An occupational form of unilateral progressive sciatic neuropathy has been described in young male farmers in India. 7 Rare intrinsic lesions of the sciatic nerve, such as neurilemomas, neurofibromas, and neurofibrosarcomas, present with chronic progressive pain and dysesthesias in the sciatic nerve distribution accompanied by varying degrees of neurological deficits and sometimes by palpable swelling along the nerve which may be visualized by CT scanning. 9 Sciatic Nerve Entrapment There are only two other reports of sciatic nerve entrapment by bands. Banerjee and Half described the case of a 34-year-old diabetic woman with posterior thigh pain and paresthesias for I year, a Tinel's sign elicited by pressure on the sciatic nerve in the thigh, absence of ankle reflex, and hypesthesia over the lateral border of the foot. A myofascial band, presumed to be developmental, was found extending from the biceps femoris to the adductor magnus muscle, constricting the sciatic nerve. Sectioning of the band was followed by relief of symptoms. S~gaard ~ described a man with a 3-year history of pain and paresthesias in the leg brought on by sitting
654
1. Baker GS, Parsons WR, Welch JS: Endometriosiswithin the sheath of the sciatic nerve. Report of two patients with progressive paralysis. J Neurosurg 25:652-655, 1966 2. Banerjee T, Hall CD: Sciatic entrapment neuropathy. Case report. J Neutosurg 45:216-217, 1976 3. Barber KW Jr, Bianco AJ Jr, Soule EH, et al: Benign extraneural soft-tissue tumors of the extremities causing compression of nerves. J Bone Joint Surg (Am) 44: 98-104, 1962 4. Dawson DM, Hallett M, Millender LH: Entrapment Neuropathies. Boston: Little. Brown & Co, 1983, pp 195-200
5. Jones BV, Ward MW: Myositis ossificans in the biceps femoris musclescausingsciatic nerve palsy. A case report. J Bone Joint Surg (Br) 62:506-507, 1980 6. Rousseau JJ, Reznik M, LeJune GN, et al: Sciatic nerve entrapment by pentazocine -- induced muscle fibrosis.A case report. Arch Neurol 36:723-724, 1970 7. Singh A, Jolly SS: Wasted leg syndrome - - a compression neuropathy of lower limbs. J Assoc Physicians India 11: 1031-1037, 1963 8. Sogaard IB: Sciatic nerve entrapment. Case report. J Neurosurg 58:275-276, 1983 9, Thomas JE, Piepgras DG, Scheithauer B, et ai: Neurogenic tumors of the sciatic nerve. A clinicopathologic study of 35 cases, Mayo Clin Pror 58:640-647, 1983
Manuscript receivedMarch 27. 1990. Accepted in final form February 20, 1991. Address reprint requests to: Nagagopal Venna, M.D., Neurological Unit, Boston City Hospital, 818 Harrison Avenue, Boston, Massachusetts 02118.
J. Neurosurg. / Volume 75 / October, 1991
Sciatic nerve entrapment in a child Case report NAGAGOPAL VENNA, M.D., M.R.C.P., M.R.C.P.(I), MARTIN BIELAWSKI, M.D., AND EDWARD M. SPA'FZ, M.D.
Neurological Unit, Boston Cit)~Hospital and Department of Neurosurgery. University Hospital, Boston University School of Medicine, Boston, Massachusetts v, A child was brought for evaluation of signs of unilateral chronic progressive sciatic nerve dysfunction found to be due to nerve entrapment in the thigh by a fibrovascularband. Sectioningof the band was followed by marked improvement in the nerve function. Compression by a band is a rare but treatable cause of sciatic neuropathy. KEY WORDS
9
sciatic nerve
9
ESIONSof the sciatic nerve trunk are rare. Most are acute, resulting from stab wounds, improperly placed intramuscular injections, or as complications of hip surgery or anticoagulant therapy? Chronic lesions of the sciatic nerve are distinctly unusual and are likely to be misdiagnosed as lesions of the nerve root or lumbosacral plexus. Moreover, if foot deformity ensues from a sciatic nerve lesion in a child, then a developmental orthopedic anomaly or developmental abnormality of the spinal cord or of the cauda equina, such as meningomyelocele or diastematomyelia, is likely to be considered rather than a peripheral nerve-trunk lesion. We describe the case of a child with sciatic nerve entrapment by a fibrovascular band in the thigh to highlight its clinical and neurophysiological features and to stress the improvement of nerve function by surgery.
L
C a s e Report
This 12-year-old boy was referred for evaluation of deformity and weakness of the right foot. The earliest indication appeared 3 years previously, when it was observed that he could not run well. Two years later, his mother noted a tendency of the right foot to turn inward while he walked, which progressed to persistent deformity and wasting of the foot. The boy complained of intermittent tingling down the posterior aspect of the right thigh and calf to the heel but denied pain. The left lower extremity and bladder and bowel control were 652
nerve entrapment
9
fibrovascular band
not affected. There was no history of recent or remote trauma to the back or to the lower extremity. Examination. The boy was healthy-looking and muscular. Abnormalities were confined to the right lower extremity: there was an equinovarus deformity of the right foot. The extensor digitorum brevis muscle, medial plantar foot intrinsic muscles, and (to a lesser extent) the calf and lower parts of the hamstring muscles were atrophied but the gluteal muscles were of normal bulk. Dorsiflexion and eversion of foot and dorsiflexion of the toes were weak, while plantar flexion and inversion of the foot were normal. Knee flexion was slightly weak. Extension of the knee and all movements at the hip were normal. Sensory examination showed blunted pinprick sensation over the lateral border of the foot. The right ankle reflex was absent. The appearance of the skin of the lumbar region and the legs and the shape and mobility of the lumbar spine were normal. No soft-tissue masses or areas of tenderness were detected in the gluteal region or in the thigh, but pressure on the sciatic nerve trunk in the mid-thigh region consistently produced a positive Tinel's sign of paresthesia down the leg. Electromyographic examination of the right lower extremity revealed moderate denervation in the long head of the biceps femoris, medial hamstring, and medial gastrocnemius muscles and mild denervation in the short head of the biceps femoris, tibialis anterior, and peroneus longus muscles (Fig. 1). No abnormalities J. Neurosurg. / Volume 75 / October, 1991
Sciatic nerve entrapment in a child
FIG. 2. Diagram showing the appearances of the sciatic nerve at surgery. The thin arrow points to the proximal end of the nerve and the broad arrow to the fibrovascularband.
FIG. 1. Diagram illustrating the innervation of the gluteal and posterior thigh muscles. The lesion of the sciatic nerve was proximal to the branches to the hamstring muscles. The gluteal muscles, supplied by the superior and inferior gluteal nerves, were spared.
were found in the gluteus maximus, gluteus medius, or the tensor fasciae latae muscles. The patient did not permit examination of the paraspinal muscles. Motor nerve conduction velocity of the posterior tibial nerve was slowed to 28 m/sec, while the motor nerve conduction of the common peroneal nerve was nearly normal. Sural nerve sensory potential, H-reflex, and F-wave responses from the common peroneal and posterior tibial nerves were absent in the right leg. The right sciatic F-wave from the knee to the gastrocnemius soleus muscle was markedly prolonged. The corresponding data from the left leg were normal. Plain radiographs, computerized tomography (CT) scans of the lumbosacral spine and pelvis, a lumbar myelogram, and magnetic resonance images of the gluteal region and thigh were normal. On the basis of the clinical and electrophysiological findings, a lesion of the right sciatic nerve proximal to the origin of the branches to the hamstring muscles in the mid-thigh region was suspected. Operation. Surgery was performed under general endotracheal anesthesia. A long incision was outlined along the projected path of the sciatic nerve over the mid-portion of the posterior aspect of the thigh and was extended superiorly and laterally around the buttock and distally into the popliteal fossa to enable exploration of the nerve in these regions if needed. The J. Neurosurg. / Volume 75/October, 1991
thigh portion of the incision was opened from the gluteal crest to the superior portion of the popliteal fossa. The space between the biceps femoris and the semi-membranosus muscles was developed and the sciatic nerve visualized. The nerve was explored in a proximal to distal direction until the pathology was identified at about the junction of the middle and distal thirds of the thigh. A firm fibrous band was found constricting the sciatic nerve (Fig. 2). The tibial component of the nerve was more severely compressed than the peroneal component. The fibrous band was resected. Inspection and palpation of the nerve revealed no intraneural lesion. Histologically, the band consisted of dense fibrous connective tissue and normal-appearing blood vessels. Postoperative Course. The paresthesias resolved the day after surgery. One month later, there was definite improvement in the strength of dorsiflexion and eversion of the foot and improvement in pinprick sensation over the lateral border of the foot. At l year, strength in all muscle groups of the lower extremity was normal, although the decreased sensation at the foot, absence of the ankle reflex, and the foot deformity persisted. Discussion Localization of the Lesion The clinical and electrophysiologicai evidence suggested a lesion of the sciatic nerve in the mid-thigh region (Fig. 1). There was wasting and weakness of the foot and leg and the hamstring muscles, while the gluteal muscles were unaffected. There was a distinct Tiners sign over the sciatic nerve in the thigh. The absence of sural nerve action potential indicated a lesion distal to the dorsal root ganglion. The absence of denervation in the gluteus maximus, gluteus medius, and the tensor fasciae latae muscles indicated sparing of the inferior and superior gluteal nerves arising directly from the lumbosacral plexus through the roots of L-4, L-5, and S-1 (these nerves accompany the sciatic
653
N. Venna, M. Bielawski, and E. M. Spatz nerve through the greater sciatic notch to the level of the pyriformis muscle). In contrast, the hamstring muscles showed denervation, indicating involvement of the sciatic nerve in the mid-thigh region from where the branches to the hamstring muscles arise. The marked slowing of the motor nerve conduction of the posterior tibial nerve suggested a lesion of the distal nerve trunk rather than of the nerve root or plexus. This also indicated more severe compromise of the tibial component of the sciatic nerve compared to the peroneal component. The sciatic nerve is submerged deeply in the gluteai region and the thigh, and is not accessible for stimulation by surface electrodes. Thus, a conduction delay across a segment of the sciatic nerve cannot be reliably measured as is possible for many superficial nerves of the limbs. Techniques are not yet generally available for the direct measurement of the motor nerve conduction velocity after stimulation of the sciatic nerve through needle electrodes and by recording somatosensory evoked potentials over different parts of the sciatic nerve, over the lumbosacral plexus, and over the spine at the root entry zones:
and relieved by standing; the pain first occurred a few months after he had fallen on his buttocks. Except for Tinel's sign over the sciatic nerve in the thigh, clinical and limited electrophysiological examinations were normal. A myofascial band was discovered at surgery across the sciatic nerve I 0 cm distal to the gluteal fold. Sectioning of the constricting band relieved the symptoms. It was postulated that the band was formed by organization of the posttraumatic hematoma. The present case shows that, if untreated, sciatic nerve compression by a band can progress to severe neurological impairment and deformity. The onset of our patient's symptoms coincided with a growth spurt at the age of 9 years, during which he became distinctly more muscular. The increase in the muscle mass of the thigh and enlargement of the sciatic nerve with growth probably contributed to compromise of the sciatic nerve already entrapped by the band. We believe that awareness of this entity and thorough clinical examination along with focused electrophysiological testing will increase the recognition of this treatable condition. References
Etiology of Sciatic Nerve Palsies Gradually evolving lesions of the sciatic nerve are rare. Extrinsic compression of the nerve has been described in relation to myositis ossificans in the biceps femoris muscle: lipomas, 3 endometriosis) and in the rare syndrome of progressive muscle fibrosis following repeated intramuscular injections of pentazocine.6 An occupational form of unilateral progressive sciatic neuropathy has been described in young male farmers in India. 7 Rare intrinsic lesions of the sciatic nerve, such as neurilemomas, neurofibromas, and neurofibrosarcomas, present with chronic progressive pain and dysesthesias in the sciatic nerve distribution accompanied by varying degrees of neurological deficits and sometimes by palpable swelling along the nerve which may be visualized by CT scanning. 9 Sciatic Nerve Entrapment There are only two other reports of sciatic nerve entrapment by bands. Banerjee and Half described the case of a 34-year-old diabetic woman with posterior thigh pain and paresthesias for I year, a Tinel's sign elicited by pressure on the sciatic nerve in the thigh, absence of ankle reflex, and hypesthesia over the lateral border of the foot. A myofascial band, presumed to be developmental, was found extending from the biceps femoris to the adductor magnus muscle, constricting the sciatic nerve. Sectioning of the band was followed by relief of symptoms. S~gaard ~ described a man with a 3-year history of pain and paresthesias in the leg brought on by sitting
654
1. Baker GS, Parsons WR, Welch JS: Endometriosiswithin the sheath of the sciatic nerve. Report of two patients with progressive paralysis. J Neurosurg 25:652-655, 1966 2. Banerjee T, Hall CD: Sciatic entrapment neuropathy. Case report. J Neutosurg 45:216-217, 1976 3. Barber KW Jr, Bianco AJ Jr, Soule EH, et al: Benign extraneural soft-tissue tumors of the extremities causing compression of nerves. J Bone Joint Surg (Am) 44: 98-104, 1962 4. Dawson DM, Hallett M, Millender LH: Entrapment Neuropathies. Boston: Little. Brown & Co, 1983, pp 195-200
5. Jones BV, Ward MW: Myositis ossificans in the biceps femoris musclescausingsciatic nerve palsy. A case report. J Bone Joint Surg (Br) 62:506-507, 1980 6. Rousseau JJ, Reznik M, LeJune GN, et al: Sciatic nerve entrapment by pentazocine -- induced muscle fibrosis.A case report. Arch Neurol 36:723-724, 1970 7. Singh A, Jolly SS: Wasted leg syndrome - - a compression neuropathy of lower limbs. J Assoc Physicians India 11: 1031-1037, 1963 8. Sogaard IB: Sciatic nerve entrapment. Case report. J Neurosurg 58:275-276, 1983 9, Thomas JE, Piepgras DG, Scheithauer B, et ai: Neurogenic tumors of the sciatic nerve. A clinicopathologic study of 35 cases, Mayo Clin Pror 58:640-647, 1983
Manuscript receivedMarch 27. 1990. Accepted in final form February 20, 1991. Address reprint requests to: Nagagopal Venna, M.D., Neurological Unit, Boston City Hospital, 818 Harrison Avenue, Boston, Massachusetts 02118.
J. Neurosurg. / Volume 75 / October, 1991
