J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.37.3.330 on 1 March 1974. Downloaded from Journal ofNeurology, , and Psychiatry, 1974, 37, 330-332

Intercostal conduction and posterior in the diagnosis and treatment of thoracic

E. RALPH JOHNSON', JOE POWELL, JAMES CALDWELL, AND CHARLES CRANE From Baylor University Medical Center, Dallas, Texas, U.S.A.

SYNOPSIS Intercostal has proved to be an accurate technique in diagnosis of thoracic radiculopathy in 161 patients, 80 of whom had subsequent posterior rhizotomy with relief of in 81% of those undergoing . The only significant complication of inter- costal nerve conduction study is an 888% incidence of pneumothorax. guest. Protected by copyright. The development of the intercostal nerve motor objective clinical signs or definitive diagnostic conduction study, a new electrodiagnostic techniques made the diagnosis of thoracic root technique for establishing a definitive diagnosis pain one of exclusion. In some cases thoracic in thoracic radiculopathy, has previously been myelography revealed a defect which established reported by Caldwell et al. (1968). The purpose the pathology. However, the majority of patients of this paper is to report five years' experience with symptoms of thoracic radiculopathy have with this technique and the results of subsequent negative myelograms. Frequently multiple diag- surgery at Baylor University Medical Center, nostic and surgical procedures were done in an Dallas, Texas. attempt to remove the pain with no specific The first 11 primary divisions ofthe 12 thoracic benefit. Posterior rhizotomy is a pain-relieving are described as intercostal nerves, with procedure (White, 1965). Neurosurgeons, how- the 12th termed the . The inter- ever, are reluctant to operate when the diagnosis costal nerves are distributed chiefly to the and level of involvement are unclear. Denerva- parietes of the and . The 1st tion potentials found in electromyographic thoracic nerve divides into two parts, one of examination of the thoracic paraspinous muscles which enters the roots of the , the might suggest the diagnosis but do not establish other becoming the first intercostal nerve. The a root level. Intercostal motor nerve conduction http://jnnp.bmj.com/ second through the 6th thoracic nerves and the study is a definitive electrodiagnostic technique intercostal section of the 1st thoracic nerve seg- in establishing the diagnosis and level of thoracic mentally innervate the thoracic wall and the radiculopathy. . The 7th through the 12th innervate the thorax and abdominal wall and METHODS intercostal muscles. The patient is placed under light anaesthesia and is or trau- on September 27, 2021 by Compression, inflammation, scarring, then positioned to lie on the uninvolved side. matic irritation of the thoracic nerve roots or Recording electromyographic needle electrodes are intercostal nerves can produce chest or ab- placed in the desired interspace in the mid-axillary dominal pain simulating cardiac, pulmonary, or line. Two 1 inch Meditron insulated monopolar abdominal disease. Previously the absence of electromyographic needles for stimulating are inserted in the corresponding interspace as near the 1 Address for reprints: Department of Physical Medicine and Re- habilitation, University of Texas Southwestern Medical School, 5323 spinal column as technically possible. The electrode Harry Hines Building, Dallas, Texas, U.S.A., 75235. tips are placed adjacent to the intercostal nerve with 330 J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.37.3.330 on 1 March 1974. Downloaded from Intercostal nerve conduction in the diagnosis of thoracic radiculopathy 331 the negative stimulation electrode located distal to tubes, with the remaining patients having 10- the . A ground electrode is placed between 20% pneumothorax requiring only bed rest for the stimulating and recording needles. Both a resolution. Because of this complication, routine Meditron Model 201-AD and TECA Model B-2 pre-study chest films are recommended and Electromyograph were used in this study. As the routine post-study chest films are necessary. The stimulus voltage is increased, the recording and incidence of pneumothorax is higher than that stimulating electrodes are adjusted to give a maximal response, which is recorded by Polaroid photo- recorded in intercostal nerve block (Moore and graphy. Time between stimulus and muscle response Bridenbaugh, 1962). is recorded in milliseconds and the photographs Opaque thoracic myelography was done on 87 screened for abnormal dispersion in the muscle patients. Thirteen (15%) of these are recorded as response. The same procedure is conducted on each positive. All patients with positive myelograms accessible intercostal nerve on the involved side of showed abnormal intercostal nerve conduction the body. It is usually possible to check levels T2-12 studies at the level of the defect. Four of the 13 in a slender individual. In an obese patient it may be patients declined surgery. Four patients with impossible to go higher than T4 or T5 intercostal herniated thoracic intervertebral discs, two nerves. After testing intercostal conduction times, with metastatic carcinoma, one with arachnoid thoracic paraspinous muscles may be examined for denervation activity by standard electromyographic cyst, and one with had a negative techniques (Nelson, 1967). The patient is then trans- myelogram with a positive conduction study. ferred to the surgical recovery room for post- anaesthetic care. SURGERY Eighty patients are recorded as having guest. Protected by copyright. had 86 surgical procedures. Seventy-one patients RESULTS went to surgery on the findings of intercostal nerve study alone with nine patients having both In the five years following the development of myelographic and intercostal conduction study intercostal conduction studies at Baylor 160 abnormalities. The following 86 surgical pro- patients (54 male and 106 female) were evaluated cedures were carried out: posterior rhizotomy for thoracic radiculopathy by this technique. or modified posterior rhizotomy (80), biopsy of The median age of these patients is 42 years with metastatic carcinoma (1), excision of thoracic a range of 12-82 years. Nine hundred and disc (1), excision of meningioma (1), excision of seventy-one intercostal nerve conduction delays (1), excision of neuroma (2). are recorded from these patients. The median The following 86 findings at surgery are conduction delay is 3-0 msec. The mean value recorded: scarring around root (19), osteophytic for those intercostal delays considered normal is or other bony entrapment (16), protruding inter- 3-1 msec. The criteria for abnormality are. vertebral disc (9), neuroma (3), microscopic 1. Delay greater than 5 0 msec with dispersion of degeneration (3), metastatic carcinoma (2), evoked response compression between transverse process and 2. Delay greater than 6-0 msec rib (2), arachnoid cyst (1), multiple myeloma (1), http://jnnp.bmj.com/ 3. Delay 2-0 msec greater than the mean delay for herpes zoster (demonstrated by electron micro- that patient scopy) (1), intradural meningioma (1), An example illustrating number 3 above is as with no surgical or microscopic evidence of follows: aetiology (28). T5 1-8 ms T9 2-1 ms Of the 74 patients undergoing posterior T6 2-0 ms T1O 4-8 ms rhizotomy 14 (19%) poor results are recorded. T7 2-1 ms ms TI1 2-0 The follow-up period ranges from one month to on September 27, 2021 by T8 2-0 ms T12 2-0 ms 14- years. A poor result was manifested by con- TIO intercostal nerve would be considered ab- tinued pain at the previous location or new pain normal. in an adjacent location. An evaluation of No deaths are reported after intercostal nerve patients with poor results fails to reveal any conduction study. The only significant complica- pattern. However, one poor result occurred in a tion was post-study pneumothorax in 14 patients patient with multiple myeloma and one in a (8.8%). Two of these patients required chest patient whose surgery was performed at a J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.37.3.330 on 1 March 1974. Downloaded from 332 E. Ralph Johnson, Joe Powell, James Caldwell, and Charles Crane different level from that recorded as abnormal that patient, or any delay greater than 6-0 ms. by intercostal conduction study. Posterior rhizotomy after localization of the The only death reported postoperatively level in thoracic radiculopathy produced relief occurred from bacterial endocarditis in a patient from pain in 81% of operated patients. During who had metastatic carcinoma. Morbidity the last year of this study, with improved selec- included one patient with pericarditis, one with tion of patients and continued experience in toxic hepatitis secondary to halothane, one with intercostal nerve conduction study technique, pulmonary embolus, and two with pneumonitis. this experience has improved, with 91% of One patient who had a thoracic disc excision patients having relief from pain. developed weakness of the left leg. REFERENCES CONCLUSION Barthakur, A., and Harden, K. A. (1961). Entrapment neuropathy of intercostal nerve. A case report. Journal of Intercostal nerve conduction study is an accurate National Medical Association, 53, 493-495. technique for the definitive diagnosis of thoracic Caldwell, J. W., Crane, C. R., and Boland, G. L. (1968). radiculopathy and for the establishment of the Determinations of intercostal motor conduction time in diagnosis of compression. Archives of Physical level involved. The only significant complication Medicine, 49, 515-518. of intercostal nerve conduction study is pneumo- Dick, E. (1961). Intercostal nerve nipping due to rib disloca- thorax which occurred in 8.8% of 160 patients tion. New Zealand Medical Journal, 60, 576-577. undergoing 971 separate intercostal nerve con- Moore, D. C., and Bridenbaugh, L. D. (1962). Pneumothorax. Its incidence following intercostal nerve block. Journal ofguest. Protected by copyright. duction studies. The median intercostal nerve the American Medical Association, 182, 1005-1008. conduction delay is 3 0 ms. The mean is 3-1 Nelson, J. W. (1967). Electromyographic examination of the ms with a erectores spinae in patients suspected of having nerve root standard deviation of 07 ms. lesions. (Abstract.) Electroencephalography and Clinical Abnormality is established by a delay greater Neurophysiology, 23, 391-392. than 5 0 ms with dispersion of evoked muscular White, J. C. (1965). Posterior rhizotomy: a possible substitute response, a delay greater than 2-0 ms more for cordotomy in otherwise intractable of the trunk and extremities of nonmalignant origin. Clinical than the mean delay for the intercostal nerves of Neurosutrgery, 13, 20-41. http://jnnp.bmj.com/ on September 27, 2021 by