ANESTH ANALG 1990;71:197-9
197
Long Thoracic Nerve Block Somayaji Ramarnurthy, MD, Rosemary Hickey, MD, Alfonso Maytorena, Joan Hoffman, RN, MSN, and Ananthal Kalantri, MD
Key Words: ANESTHETIC TECHNIQUES, REGIONAL-long thoracic nerve block. Seven patients with intractable pain of the lateral chest wall under the axilla appeared to have pain originating from spasm of the serratus anterior muscle. A long thoracic nerve block to interrupt selectively the innervation to this muscle could confirm this diagnosis, but a review of the literature revealed no previous reports of this type of block. After reviewing the anatomy, a technique for long thoracic nerve block was developed.
Methods Anatomy The long thoracic nerve arises from the anterior branches of the C5, C6, and C7 nerve roots and rarely (8%) from C8 (1). This nerve usually innervates a single muscle, the serratus anterior. It provides no cutaneous innervation. As described by Honvitz and Tocantins (l),the first two roots enter the middle scalene muscle, unite, and join the C7 root. The long thoracic nerve then descends dorsally to the brachial plexus and down the anterolateral aspect of the chest wall (2). It sends branches to all the digitations of the serratus anterior muscle (2). In some instances (5%) the root from C5 may course independently of the others to be distributed to the upper digitations of the serratus anterior (1). Other anatomic variations include those in which the C7 root (8%) is absent or unites with the C5 and C6 roots below the clavicle (13%)(1).
Received from The University of Texas, Health Science Center at San Antonio, San Antonio, Texas. Accepted for publication April 19, 1990. Address correspondence to Dr. Rarnarnurthy, The University of Texas, Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78284-7838. 01990 by the International Anesthesia Research Society
MD,
Technique The patient is placed in the supine position without a pillow and instructed to raise his or her head to facilitate palpation of the sternocleidomastoid muscle by making it more prominent. After palpation of the posterior border of the sternocleidomastoid muscle with the index finger, the patient is instructed to lower the head and to relax the neck muscles. The index and middle fingers of the anesthesiologist’s palpating hand are then rolled laterally to identify the anterior scalene muscle, the interscalene groove, and the middle scalene muscle. The index and middle fingers are then placed on the middle scalene muscle and a 22-gauge 3-cm regional block needle (short bevel) attached to a nerve stimulator is slowly advanced into the muscle in a direction that parallels the long axis of the middle scalene muscle, in a direction that is caudad and slightly lateral (Figure 1). The muscle is entered just above the level of C6, which is determined by noting the level of the cricoid cartilage. The lateral chest wall over the serratus anterior muscle is exposed to observe muscle contractions, and, in addition, an assistant attempts to identify contractions induced with the nerve stimulator by placing his hand over the area of the muscle. If contraction of the trapezius muscle occurs, indicating stimulation of the spinal accessory nerve, the needle is redirected more anteriorly to locate the long thoracic nerve. The final needle position is maintained at the point where maximum contraction of the serratus anterior muscle is noted. After negative aspiration, 5 mL of local anesthetic solution (0.5% bupivacaine) is injected. To evaluate the motor effect of the block, the strength of the serratus anterior muscle should be evaluated before and after the block. One function of the serratus anterior is to connect the third, fourth, and fifth ribs with the vertebral border of the scapula and draw the scapula forward (3). When muscle function is impaired, the vertebral border of the scapula protrudes dorsomedially, the shoulder
198
ANESTH ANALG 1990;71:197-9
CLINICAL REPORTS
I
sole innervation of consequence of this muscle. The above technique was developed and utilized in this patient. The patient was examined by a physical therapist before and after the block. Although no weakness of the serratus anterior muscle was present before the block, pronounced scapular winging was present at 30 min after the block. Also, at 30 min after the block the patient reported complete relief of pain, which he had described as severe before the block. He was instr-ucted in a home program of gentle stretching exercises for the serratus anterior muscle. On followup, the patient reported no return of pain for 1 mo. After 1 mo, however, the pain gradually returned until at 1.5 mo, the pain had returned to the original level. The block was subsequently performed in six patients with confusing pain problems, all with pain below the axilla on the chest wall. Motor block of the serratus anterior was confirmed after the block in each patient by the presence of scapular winging. Electromyography was also utilized in two patients to further document that the block effectively interrupted innervation of the serratus anterior muscle. Before the block, normal motor unit activity was noted on electromyography. After the block, voluntary motor unit activity was abolished, indicating motor block. Of the six patients in which the block was utilized, four had excellent pain relief, suggesting that most or all of their pain originated from the serratus anterior muscle. These patients had pain relief that outlasted the effective duration of action of the local anesthetic. One patient reported only partial pain relief, but it was believed that her pain was more diffuse, originating not only from the serratus anterior muscle but also from other adjacent structures. The one patient who reported no pain relief from the block had had a thoracotomy, and subsequent injection of local anesthetic into his thoracotomy scar resulted in good pain relief. The only complications that were seen from the block were hypesthesia in the cutaneous distribution of branches of the cervical plexus. In all seven patients, hypesthesia was noted in the cutaneous distribution of the supraclavicular nerves, and in two patients hypesthesia in the distribution of the lesser and greater occipital nerves was noted.
tenor Scalene m
Figure 1. The long thoracic nerve, which innervates the serratus anterior muscle, is blocked as it pierces the middle scalene muscle.
droops, and the arm cannot be abducted beyond 90” (4). The protrusion of the scapula is referred to as scapular “winging” and is accentuated when the arm is pressed against a wall and an attempt is made to push the body away from the wall (4). When the block is performed to relieve muscular spasm, gentle stretching exercises also should be given to the patient in an attempt to prevent return of the spasm.
Report of Seven Cases A 36-yr-old man presented with the complaint of pain in the right lateral chest wall under the axilla after a twisting, pulling injury to the muscle. Chest x-ray after the injury revealed no rib fractures. He had received physical therapy, multiple trigger point injections, and intercostal nerve injections, including neurolytic intercostal blocks. Each of these treatments resulted in only partial relief of his pain, and thus relief was only temporary (several hours to less than a week). On physical examination good strength of the serratus anterior muscle was noted as well as hypesthesia over the painful area due to the previous neurolytic intercostal blocks. The pain appeared to be originating from the serratus anterior muscle and to be due to spasm of that muscle. It was believed that a block of the long thoracic nerve could help establish the diagnosis because the long thoracic nerve is the
Discussion The technique described for blocking the long thoracic nerve is relatively simple and safe. It provides a useful diagnostic and therapeutic block of the serra-
CLINICAL REPORTS
tus anterior muscle. Although the necessity to block this muscle may arise only infrequently, there are select patients, such as the ones we described, for whom knowledge of this technique may prove extremely beneficial. It should be noted that even though we have described the long thoracic nerve solely as a motor nerve, it may also transmit sensory information from its muscular innervation, the serratus anterior. This may help to explain its usefulness in the relief of pain originating from spasm of this muscle. We had few complications associated with this block, We did note block of branches of the superficial cervical plexus, which lie under the posterior border of the sternocleidomastoid muscle. The use of a smaller volume of local anesthetic may decrease the likelihood of block of these nerves. Although not noted in our patients, local anesthetic spread resulting in block of the dorsal scapular nerve (innervator of rhomboids and Ievator scapula) and the spinal accessory nerve (innervator of the sternocleidomastoid and trapezius) may also be possible in view of their close proximity to the long thoracic nerve. Anatomic variations in which the C5 root courses independently into the muscle or in which the C7 root joins the nerve below the clavicle may lead to only partial block, if the local anesthetic does not spread to these roots. Even partial block, however, may be beneficial in the relief of pain from muscular spasm.
ANESTH ANALG 1990:71:197-9
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Knowledge of the relationship between the long thoracic nerve and brachial plexus roots may be helpful in performing a brachial plexus block. If the serratus anterior is stimulated in an attempt to locate the brachial plexus trunks (subclavian perivascular block) or roots (interscalene block), the needle should be redirected more anteriorly. Likewise, if during performance of a long thoracic nerve block the brachial plexus is stimulated, the needle should be redirected more dorsally to locate the long thoracic nerve. In conclusion, no previous reports are available for block of the long thoracic nerve, and the technique that we have described is relatively simple and associated with few complications.
References 1. Horwitz MT, Tocantins LM. An anatomical study of the role of the long thoracic nerve and the related scapular bursae in the pathogenesis of local paralysis of the serratus anterior muscle. Anat Rec 1938;71:375-85.
2. Gray H. The peripheral nervous system. In: Clemente CD, ed. Anatomy of the human body. Philadelphia: Lea and Febiger, 19851209. 3. Gregg JR, Labosky D, Harty M, et al. Serratus anterior paralysis in the young athlete. J Bone Joint Surg 1979;61:825-32. 4. Martin JT. Postoperative isolated dysfunction of the long tho-
racic nerve: a rare entity of uncertain etiology. Anesth Analg 1989;69:614-9.
197
Long Thoracic Nerve Block Somayaji Ramarnurthy, MD, Rosemary Hickey, MD, Alfonso Maytorena, Joan Hoffman, RN, MSN, and Ananthal Kalantri, MD
Key Words: ANESTHETIC TECHNIQUES, REGIONAL-long thoracic nerve block. Seven patients with intractable pain of the lateral chest wall under the axilla appeared to have pain originating from spasm of the serratus anterior muscle. A long thoracic nerve block to interrupt selectively the innervation to this muscle could confirm this diagnosis, but a review of the literature revealed no previous reports of this type of block. After reviewing the anatomy, a technique for long thoracic nerve block was developed.
Methods Anatomy The long thoracic nerve arises from the anterior branches of the C5, C6, and C7 nerve roots and rarely (8%) from C8 (1). This nerve usually innervates a single muscle, the serratus anterior. It provides no cutaneous innervation. As described by Honvitz and Tocantins (l),the first two roots enter the middle scalene muscle, unite, and join the C7 root. The long thoracic nerve then descends dorsally to the brachial plexus and down the anterolateral aspect of the chest wall (2). It sends branches to all the digitations of the serratus anterior muscle (2). In some instances (5%) the root from C5 may course independently of the others to be distributed to the upper digitations of the serratus anterior (1). Other anatomic variations include those in which the C7 root (8%) is absent or unites with the C5 and C6 roots below the clavicle (13%)(1).
Received from The University of Texas, Health Science Center at San Antonio, San Antonio, Texas. Accepted for publication April 19, 1990. Address correspondence to Dr. Rarnarnurthy, The University of Texas, Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78284-7838. 01990 by the International Anesthesia Research Society
MD,
Technique The patient is placed in the supine position without a pillow and instructed to raise his or her head to facilitate palpation of the sternocleidomastoid muscle by making it more prominent. After palpation of the posterior border of the sternocleidomastoid muscle with the index finger, the patient is instructed to lower the head and to relax the neck muscles. The index and middle fingers of the anesthesiologist’s palpating hand are then rolled laterally to identify the anterior scalene muscle, the interscalene groove, and the middle scalene muscle. The index and middle fingers are then placed on the middle scalene muscle and a 22-gauge 3-cm regional block needle (short bevel) attached to a nerve stimulator is slowly advanced into the muscle in a direction that parallels the long axis of the middle scalene muscle, in a direction that is caudad and slightly lateral (Figure 1). The muscle is entered just above the level of C6, which is determined by noting the level of the cricoid cartilage. The lateral chest wall over the serratus anterior muscle is exposed to observe muscle contractions, and, in addition, an assistant attempts to identify contractions induced with the nerve stimulator by placing his hand over the area of the muscle. If contraction of the trapezius muscle occurs, indicating stimulation of the spinal accessory nerve, the needle is redirected more anteriorly to locate the long thoracic nerve. The final needle position is maintained at the point where maximum contraction of the serratus anterior muscle is noted. After negative aspiration, 5 mL of local anesthetic solution (0.5% bupivacaine) is injected. To evaluate the motor effect of the block, the strength of the serratus anterior muscle should be evaluated before and after the block. One function of the serratus anterior is to connect the third, fourth, and fifth ribs with the vertebral border of the scapula and draw the scapula forward (3). When muscle function is impaired, the vertebral border of the scapula protrudes dorsomedially, the shoulder
198
ANESTH ANALG 1990;71:197-9
CLINICAL REPORTS
I
sole innervation of consequence of this muscle. The above technique was developed and utilized in this patient. The patient was examined by a physical therapist before and after the block. Although no weakness of the serratus anterior muscle was present before the block, pronounced scapular winging was present at 30 min after the block. Also, at 30 min after the block the patient reported complete relief of pain, which he had described as severe before the block. He was instr-ucted in a home program of gentle stretching exercises for the serratus anterior muscle. On followup, the patient reported no return of pain for 1 mo. After 1 mo, however, the pain gradually returned until at 1.5 mo, the pain had returned to the original level. The block was subsequently performed in six patients with confusing pain problems, all with pain below the axilla on the chest wall. Motor block of the serratus anterior was confirmed after the block in each patient by the presence of scapular winging. Electromyography was also utilized in two patients to further document that the block effectively interrupted innervation of the serratus anterior muscle. Before the block, normal motor unit activity was noted on electromyography. After the block, voluntary motor unit activity was abolished, indicating motor block. Of the six patients in which the block was utilized, four had excellent pain relief, suggesting that most or all of their pain originated from the serratus anterior muscle. These patients had pain relief that outlasted the effective duration of action of the local anesthetic. One patient reported only partial pain relief, but it was believed that her pain was more diffuse, originating not only from the serratus anterior muscle but also from other adjacent structures. The one patient who reported no pain relief from the block had had a thoracotomy, and subsequent injection of local anesthetic into his thoracotomy scar resulted in good pain relief. The only complications that were seen from the block were hypesthesia in the cutaneous distribution of branches of the cervical plexus. In all seven patients, hypesthesia was noted in the cutaneous distribution of the supraclavicular nerves, and in two patients hypesthesia in the distribution of the lesser and greater occipital nerves was noted.
tenor Scalene m
Figure 1. The long thoracic nerve, which innervates the serratus anterior muscle, is blocked as it pierces the middle scalene muscle.
droops, and the arm cannot be abducted beyond 90” (4). The protrusion of the scapula is referred to as scapular “winging” and is accentuated when the arm is pressed against a wall and an attempt is made to push the body away from the wall (4). When the block is performed to relieve muscular spasm, gentle stretching exercises also should be given to the patient in an attempt to prevent return of the spasm.
Report of Seven Cases A 36-yr-old man presented with the complaint of pain in the right lateral chest wall under the axilla after a twisting, pulling injury to the muscle. Chest x-ray after the injury revealed no rib fractures. He had received physical therapy, multiple trigger point injections, and intercostal nerve injections, including neurolytic intercostal blocks. Each of these treatments resulted in only partial relief of his pain, and thus relief was only temporary (several hours to less than a week). On physical examination good strength of the serratus anterior muscle was noted as well as hypesthesia over the painful area due to the previous neurolytic intercostal blocks. The pain appeared to be originating from the serratus anterior muscle and to be due to spasm of that muscle. It was believed that a block of the long thoracic nerve could help establish the diagnosis because the long thoracic nerve is the
Discussion The technique described for blocking the long thoracic nerve is relatively simple and safe. It provides a useful diagnostic and therapeutic block of the serra-
CLINICAL REPORTS
tus anterior muscle. Although the necessity to block this muscle may arise only infrequently, there are select patients, such as the ones we described, for whom knowledge of this technique may prove extremely beneficial. It should be noted that even though we have described the long thoracic nerve solely as a motor nerve, it may also transmit sensory information from its muscular innervation, the serratus anterior. This may help to explain its usefulness in the relief of pain originating from spasm of this muscle. We had few complications associated with this block, We did note block of branches of the superficial cervical plexus, which lie under the posterior border of the sternocleidomastoid muscle. The use of a smaller volume of local anesthetic may decrease the likelihood of block of these nerves. Although not noted in our patients, local anesthetic spread resulting in block of the dorsal scapular nerve (innervator of rhomboids and Ievator scapula) and the spinal accessory nerve (innervator of the sternocleidomastoid and trapezius) may also be possible in view of their close proximity to the long thoracic nerve. Anatomic variations in which the C5 root courses independently into the muscle or in which the C7 root joins the nerve below the clavicle may lead to only partial block, if the local anesthetic does not spread to these roots. Even partial block, however, may be beneficial in the relief of pain from muscular spasm.
ANESTH ANALG 1990:71:197-9
199
Knowledge of the relationship between the long thoracic nerve and brachial plexus roots may be helpful in performing a brachial plexus block. If the serratus anterior is stimulated in an attempt to locate the brachial plexus trunks (subclavian perivascular block) or roots (interscalene block), the needle should be redirected more anteriorly. Likewise, if during performance of a long thoracic nerve block the brachial plexus is stimulated, the needle should be redirected more dorsally to locate the long thoracic nerve. In conclusion, no previous reports are available for block of the long thoracic nerve, and the technique that we have described is relatively simple and associated with few complications.
References 1. Horwitz MT, Tocantins LM. An anatomical study of the role of the long thoracic nerve and the related scapular bursae in the pathogenesis of local paralysis of the serratus anterior muscle. Anat Rec 1938;71:375-85.
2. Gray H. The peripheral nervous system. In: Clemente CD, ed. Anatomy of the human body. Philadelphia: Lea and Febiger, 19851209. 3. Gregg JR, Labosky D, Harty M, et al. Serratus anterior paralysis in the young athlete. J Bone Joint Surg 1979;61:825-32. 4. Martin JT. Postoperative isolated dysfunction of the long tho-
racic nerve: a rare entity of uncertain etiology. Anesth Analg 1989;69:614-9.
