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Myeloradiculopathy: C8 and T1 radiculopathy
Author's Accepted Manuscript
Myeloradiculopathy: C8 And T1 Radiculopathy Michael P. Kelly MD, Lindley B. Wall MD, Geoffrey E. Stoker BS, K. Daniel Riew MD
www.elsevier.com/locate/enganabound
PII: DOI: Reference:
S1040-7383(14)00024-0 http://dx.doi.org/10.1053/j.semss.2014.05.008 YSSPS480
To appear in: Seminars in Spine Surgery
Cite this article as: Michael P. Kelly MD, Lindley B. Wall MD, Geoffrey E. Stoker BS, K. Daniel Riew MD, Myeloradiculopathy: C8 And T1 Radiculopathy, Seminars in Spine Surgery, http://dx.doi.org/10.1053/j.semss.2014.05.008 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Myeloradiculopathy: C8 And T1 Radiculopathy Michael P. Kelly, MD1, Lindley B. Wall, MD1, Geoffrey E. Stoker, BS2, K. Daniel Riew, MD1 1
Washington University School of Medicine, Department of Orthopedic Surgery, Saint Louis, MO
2
Washington University School of Medicine, Saint Louis, MO
From Washington University School of Medicine, Department of Orthopedic Surgery No funding support. Reprint requests Michael P. Kelly, MD Department of Orthopedic Surgery IOH 5th Floor, Box 8233 660 South Euclid Avenue Saint Louis, MO 63110 Abstract Objective: To review the diagnosis and treatment of C8 and T1 radiculopathies. Findings: Due rarity and to overlap in sensory and motor contributions, diagnosis of C8 and T1 radiculopathies may be difficult. This may also be due, in part, to an incomplete knowledge and understanding of the brachial plexus and peripheral nerve anatomy. The C8 and T1 nerves provide sensory innervation proximal to the wrist, which is important when distinguishing between these radiculopathies and an ulnar compressive lesion. Conclusions: Understanding plexus anatomy will allow surgeons to distinguish between C8 and T1 radiculopathies, with particular attention to other pathologies which present with similar complaints.
Introduction Cervical spondylosis or herniated nucleus pulposus causing radiculopathy or myeloradiculopathy is among the most common pathologies treated in a spine surgery clinic. The most commonly affected levels are C5‐C6, C6‐C7, and C4‐C5, respectively1 Far less common is C7‐T1 and T1‐T2 pathology, causing a C8 or T1 radiculopathy, with a prevalence of 6.2% of affected nerve roots in one series.1 Cervical pathologies causing these radiculopathies include herniated nucleus pulposus and cervical spondylosis. Less common causes of C8/T1 radiculopathy include tumors, for example Pancoast tumors.2 Additionally, a small number of patients may present with no evidence of spinal pathology at C7‐T1.3 When evaluating patients with upper extremity pain, one must exclude other potential pathologies such as shoulder or peripheral compressive neuropathies. With particular respect to C8 radiculopathy, compressive lesions of the ulnar nerve, such as cubital tunnel or Guyon’s canal syndrome, may cause similar presenting complaints and symptoms. This is an important point to emphasize, as spine surgeons have been shown to have difficulty differentiating between ulnar nerve pathologies and pure C8 pathologies.4 The purpose of the paper presented here is to review C8 anatomy and the diagnosis and management of C8/T1 radiculopathy. Anatomy The brachial plexus is comprised of the ventral rami of the 5th cervical nerve root through the 1st thoracic nerve root and is formed by the 13th week of gestation. In some cases, contribution from the 4th cervical root may create a “prefixed” brachial plexus or, conversely, the 2nd thoracic root may contribute to the plexus, creating a “postfixed” brachial plexus.5‐7BRACHIAL PLEXUS IMAGE(Figure 1) In these cases, the additional root contribution may be the cause of discrepancies between radiographic pathologies and dermatomal symptoms. The 8th cervical root terminates in the median nerve, the ulnar nerve, the medial brachial cutaneous and the medial antebrachial cutaneous nerves. Understanding the dermatomes and myotomes related to these three terminal branches and C8 is essential to making the proper diagnosis. A survey of spine surgeons has shown that a thorough knowledge and understanding of this anatomy is uncommon.4
C8
C8 exits the cervical spine between the C7 and T1 vertebra, providing branches to the median nerve, the ulnar nerve and the medial antebrachial nerve. As such, there may be confusion regarding which nerve is affected. C8 provides sensory innervation to the medial arm, medial (ulnar) forearm, and the ring and small fingers. Neither the median nerve nor the ulnar nerve provide sensory innervation proximal to the wrist, a key point when discriminating a C8 radiculopathy from a peripheral compressive neuropathy, like cubital tunnel syndrome.
C8 provides some motor innervation to nearly all muscles of the hand and forearm. Of particular note are the abductor pollicis brevis, superficial head of the flexor pollicis brevis, opponens pollicis, and the lateral lumbricals. These intrinsic muscles of the hand receive C8 innervation, provided by the median nerve and not the ulnar nerve. This distinction is important when one is evaluating a C8 radiculopathy versus an ulnar compressive lesion. The abductor pollicis brevis is responsible for the majority of opposition and is tested by instructing the patient to raise the thumb 90 degrees to the plane of the palm. The flexor pollicis brevis is responsible for flexion of the proximal phalanx of the thumb. Opponens pollicis abducts and flexes the first metacarpal and is tested by instructing the patient to touch the tip of the thumb to the small finger. The lumbricals are responsible for, and tested by, flexion of the metacarpophalangeal joints while maintaining extension at the interphalangeal joints.
T1
The T1 nerve root exits between the first and second thoracic vertebra and also provides branches to the median, ulnar, brachial cutaneous and antebrachial cutaneous nerves. As previously noted, neither the median nor the ulnar nerve provide sensory innervation proximal to the forearm. Again, this point is important when discriminating between a cervical pathology and some peripheral, compressive pathology. The sensory disturbance associated with a T1 radiculopathy may affect the axilla, while this is uncommon with a C8 radiculopathy. The motor weakness associated with a T1 radiculopathy may be most profoundly observed in weakness of the abductor digiti minimi. The overlap between C8 motor innervation and T1 motor innervation may make the diagnosis difficult, however. Sympathetic innervation to the face comes from T1, and not C8, and a Horner’s syndrome (ptosis, meiosis, anhydrosis) may be seen with these lesions and this may be the most telling symptom of T1 pathology.
Ulnar Nerve
A peripheral compressive neuropathy of the ulnar nerve may be confused with a C8 radiculopathy. The ulnar nerve provides sensory innervation to the ulnar border of the hand, the small finger, and the ulnar half of the ring finger. There is no ulnar contribution to the sensory innervation proximal to the wrist. The dorsal ulnar aspect of the hand receives innervation from the dorsal sensory branch of the ulnar nerve, which originates proximal to the wrist. Thus, a palmar sensory disturbance is concerning for a distal compression at Guyon’s canal. A sensory disturbance to the palmar and dorsal ulnar border of the hand and small finger suggests a compression of the ulnar nerve proximal to the branching of the dorsal sensory branch at the cubital tunnel. However, ulnar nerve compression will not cause a sensory disturbance in the forearm or arm. The ulnar nerve innervates the majority of the intrinsic muscles of the hand, though does not provide innervation to the abductor pollicis brevis, superficial head of the flexor pollicis brevis, opponens pollicis, nor the lateral lumbricals as previously mentioned. Knowing this will allow surgeons to distinguish ulnar nerve pathology from C8 pathology. An exception to this may occur in cases of Marinacci communications, where a forearm ulnar nerve to median nerve pathway exists; other similar, though rare, anatomic variations are the Riche‐Cannieu anastomosis (deep ulnar to recurrent median) and the Berretini anastomosis (communications between
common digital nerves).8 Common areas of ulnar nerve compression include the cubital tunnel and Guyon’s canal.
Median Nerve
The median nerve supplies innervation to the remainder of the hand: specifically sensation to the palmar and dorsal thumb, index, long and radial ring fingers. Median nerve pathology will not cause a sensory deficit in the forearm, as this is innervated by the lateral antebrachial cutaneous nerve, a branch of the musculocutaneous nerve. In addition to innervating the muscles of the volar forearm, the median nerve innervates the abductor pollicis brevis, superficial head of the flexor pollicis brevis, opponens pollicis, and the lateral lumbricals. There are a number of areas where pathologic compression of the median nerve may occur, though the carpal tunnel is the most common. Diagnosis Physical Examination As with any examination, a complete and thorough history should be taken. This will provide the surgeon with information that may suggest pathologies aside from C8 radiculopathy or a peripheral compressive neuropathy, such as diabetic neuropathy or a rheumatologic diagnosis. Inciting events as well as pain modifying activities should be sought. The Spurling maneuver may be useful when diagnosing a cervical radiculopathy.9 Extension of the neck and lateral bending to the ipsilateral side of the pain may create concordant pain, while flexion and lateral bending to the contralateral side will provide relief.10 The Spurling maneuver is useful to help determine those patients that are candidates for a laminoforaminotomy, rather than some other procedure. If the Spurling maneuver is not positive, particularly if there is no relief with flexion, then enlarging the foramen via laminoforaminotomy is unlikely to provide significant benefit to the patient. The shoulder abduction test is performed by abducting the affected limb past 90 degrees.This maneuver relaxes the tension on the brachial plexus and thus can relieve pain. Specific commonly used provocative tests performed in the arm include the Tinel’s test and Phalen’s test. The Tinel’s is performed by percussing along the course of the affected nerve (median or ulnar) to elicit paresthesias in the dermatome of the nerve. Phalen’s compression test is performed by instructing the patient to hold both hands and fingers in flexion, to increase carpal tunnel pressure and provoke signs of a median neuropathy. Inspection of the hand should examine for wasting of the thenar, hypothenar, and lumbrical musculature. Isolated thenar wasting may suggest a median nerve lesion, while isolated hypothenar wasting may suggest an ulnar nerve lesion. Mixed wasting may suggest a C8 lesion, including profound wasting of the intrinsics as seen in myelopathy hand. Myelopathy hand is rarely seen without pathology cranial to C6‐C7, however. Signs and symptoms of myelopathy, including ataxia, hyperreflexia, and pathologic reflexes should be investigated, as a C8 radiculopathy may exist in the setting of a myeloradiculopathy. Electrodiagnostic Studies
Electrodiagnostic studies may be useful in determining pure radiculopathy, pure peripheral neuropathy, and mixed, so‐called “double crush”, pathologies. These studies are also useful in determining other symptomatic spinal levels, which may be contributing to the symptoms, such as C7 or T1. Electromyography studies (EMG) are particularly useful when evaluating a radiculopathy, as they can help localize motor changes to a single level. The muscle groups consistently associated with a C8 radiculopathy, are the first dorsal interosseous, abductor digit minimi, abductor pollicis brevis, flexor pollicis longus, and extensor indicis proprius.11 When an EMG is performed, the paraspinal musculature should be examined as well. The paraspinals receive motor innervation from the ipsilateral dorsal rami of the exiting root. These fibers can be compressed only at the foramen and not in a peripheral neuropathy, though asymptomatic patients can have EMG changes in the cervical paraspinals.12 Nerve conduction studies (NCS) are used to evaluate for evidence of demyelinating disease or sensory conduction abnormalities, as may be seen in cubital tunnel syndrome. A cervical radiculopathy should not have abnormal NCS in the absence of a peripheral lesion. NCS will also help determine the presence of a “double crush” pattern, where there is a concomitant compression at the cervical level and at a distal site.13 Concomitant disease has been reported in approximately 10‐20% of patients.14,15 In both EMG and NCS, clinical suspicion should drive the diagnosis, as false positives and negatives are common.(AAEM, Muscle Nerve 1999) Imaging The radiographic evaluation of a C8 radiculopathy should include plain radiographs, with anteroposterior, lateral, and oblique images. The C7‐T1 level may be difficult to visualize, depending on the position of the sternum and the shoulders, though one should look for evidence of degenerative disease, particularly foraminal stenosis due to bone spurs and/or hypertrophy of the superior facet of T1. One should notice the level of the manubrium relative to the cervical spine when planning an anterior approach for management of a C8 radiculopathy.(Figure 2) In rare cases, access to the C7‐T1 disc may be difficult. Flexion and extension lateral radiographs will allow for evaluation of instability at the C7‐T1 segment and will give some information about the rigidity of the segments cranial to C7‐T1. In the authors’ experience, C8 radiculopathies may exist at segments without severe radiographic disease if they are below rigid lever arms, either severe spondylosis or a cervical fusion. Magnetic resonance imaging (MRI) is useful for evaluation of nerve root compression, particularly those caused by disc herniations. As with electrodiagnostics, clinical suspicion should drive the diagnosis, as asymptomatic changes are common on MRI.16 Not to be neglected on the MRI is the anatomy of the vertebral artery. Whether approaching the cervical spine from an anterior or posterior approach, the surgeon must always know the anatomy of the vertebral artery. While most will enter the cervical spine at C6 (92%), a small number will enter the foramen transversarium at C7 (0.6%).17 Computed tomography scanning is useful to evaluate bony anatomy, including the facet joints, as hypertrophy of either joint will contribute to foraminal stenosis.(Figures 3A,B) As with the lateral radiograph, the mid‐sagittal CT cut can provide information about the extent of distal exposure that is possible without an osteotomy of the manubrium. A CT myelogram provides useful information
regarding neural compression, but is more invasive than an MRI and is used when MRI is contraindicated.18 When evaluating areas of compression, one must remember that a nerve root may be affected by a large paracentral disc herniation at the segment cranial to its exit, particularly in a pre‐ fixed brachial plexus.3 Thus, a large C6‐C7 disc herniation may cause a C8 radiculopathy. Similarly, in a post‐fixed brachial plexus, pathology at the T1‐T2 level, affecting the T1 nerve root, may cause symptoms consistent with a C8 radiculopathy. CT Scanning is useful, though not perfect, for evaluating the success of prior fusion procedures, as pseudarthrosis may not be detected on plain films and may be the cause of a radiculopathy.19 Hehir et al. have published a series of 31 patients with C8 radiculopathy, as confirmed by EMG. They found that nerve root compression at the C7‐T1 level was inconsistent, observed in only 16% of patients. Compression at the C7 nerve root was observed in 16% of patients and at the T1 nerve root in 3% of patients. These findings suggest that a pre‐fixed or post‐fixed brachial plexus may present with C8 radiculopathy in the absence of C7‐T1 pathology. Nearly one third of the patients in this series had no specific findings. This mirrors our experience in a number of patients with C8 radiculopathy in the absence of radiographic compression. (Figure 4) Management
Nonoperative
The natural history of cervical radiculopathies, particularly those due to a herniated nucleus pulposus, has not been studied as thoroughly as lumbar disease. Nonetheless, non‐operative management for 6‐8 weeks should be considered the minimum prior to surgical intervention; the majority of patients will improve within 3 months and thus avoid surgery.1 Therefore, in the absence of incapacitating pain refractory to non‐operative interventions, such as epidural steroid injections, progressive neurologic deficits, or static motor or sensory deficits that would be deemed troublesome by the patient should they become permanent, we recommend non‐operative treatment for at least 3 months. If there is constant numbness that would bother the patient if it became permanent or profound weakness (grade 2/5), we offer surgery to decompress the affected root as quickly as possible, to prevent permanent damage. We also recommend early surgery if there is weakness of the intrinsic hand muscles due to C8‐T1 radiculopathy, as these typically take longer to improve than more proximately innervated muscles. Transforaminal epidural steroid injections are useful and are used for both therapeutic and diagnostic purposes. As noted previously, radiographic abnormalities are common and a multitude of pathologies may produce distal arm pain, so pain relief from a C8 nerve root block is confirmatory of radiculopathy and provides valuable data to the treating surgeon. Other nonoperative treatments may include physical therapy and cervical traction exercises. These interventions have not been well studied and their effectiveness is unknown, though short term results appear good.20
Operative
In our experience, operative management of C8/T1 radiculopathies is no different from other cervical radiculopathy. We reserve laminoforaminotomies for those patients with a primary complaint of arm pain, no evidence of segmental instability (including kyphosis), and a positive Spurling maneuver. As
noted before, the latter is the primary driver of indicating laminoforaminotomies in our practice. The remaining patients may be treated with anterior or posterior decompression and fusion procedures (e.g. anterior cervical discectomy and fusion) or with cervical total disc arthroplasty. Conclusion C8 and T1 Radiculopathies are uncommon and this may account for some of the difficulty observed in the diagnosis and management of this pathology. A careful physical examination will often reveal C8 radiculopathy, ulnar compressive neuropathies, and “double crush” syndromes. Surgeons must know the different presentations of these pathologies. An ulnar neuropathy will not affect the forearm sensory examination, while a C8 radiculopathy may. A T1 radiculopathy may cause sensory deficits as high as the axilla, which would be uncommon with a C8 lesion. Similarly, no thenar musculature receives innervation from the ulnar nerve, so examination of the LOAF (Lateral Lumbricals, Opponens pollicis, Abductor pollicis brevis, superficial head of Flexor pollicis brevis) is mandatory and will help distinguish C8 pathology from ulnar nerve pathology. A T1 pathology may manifest with profound intrinsic weakness, particularly with the abductor digiti minimi. The radiographic findings may be obvious or nonexistent. We have diagnosed and treated, successfully, patients with C8 radiculopathy in the absence of radiographic findings. Often these patients have a rigid lever arm above the C7‐T1 segment. Electrodiagnostics may offer some valuable information, but the history and physical examination must drive the diagnosis. Selective nerve root blocks or transforaminal epidural steroid injections may be both therapeutic and diagnostic. A small sampling of spine surgeons showed knowledge gaps regarding the myotomes and dermatomes associated with the C8/T1 nerve root and the ulnar nerve. Any surgeon treating arm pain, whether radiculopathy or neuropathy, should know and understand the commonalities and differences. Radiographic studies and electrodiagnostics may support a diagnosis, but in a small number of cases the diagnosis is made by the history and physical examination. Once the diagnosis of C8/T1 radiculopathy is made, management is consistent with other cervical radiculopathies.
1. Radhakrishnan K, Litchy WJ, O'Fallon WM, Kurland LT. Epidemiology of cervical radiculopathy. A population‐based study from Rochester, Minnesota, 1976 through 1990. Brain : a journal of neurology 1994;117 ( Pt 2):325‐35. 2. Vargo MM, Flood KM. Pancoast tumor presenting as cervical radiculopathy. Archives of physical medicine and rehabilitation 1990;71:606‐9. 3. Hehir MK, Figueroa JJ, Zynda‐Weiss AM, Stanton M, Logigian EL. Unexpected neuroimaging abnormalities in patients with apparent C8 radiculopathy: broadening the clinical spectrum. Muscle & nerve 2012;45:859‐65. 4. Stoker GE, Kim HJ, Riew KD. Differentiating c8‐t1 radiculopathy from ulnar neuropathy: a survey of 24 spine surgeons. Global spine journal 2014;4:1‐6. 5. Pandey SK, Shukla VK. Anatomical variations of the cords of brachial plexus and the median nerve. Clinical anatomy 2007;20:150‐6.
6. Johnson EO, Vekris M, Demesticha T, Soucacos PN. Neuroanatomy of the brachial plexus: normal and variant anatomy of its formation. Surgical and radiologic anatomy : SRA 2010;32:291‐7. 7. Kuzma SA, Doberstein ST, Rushlow DR. Postfixed brachial plexus radiculopathy due to thoracic disc herniation in a collegiate wrestler: a case report. Journal of athletic training 2013;48:710‐5. 8. Dogan NU, Uysal, I.I., Seker, M. The communications between the ulnar and median nerves in upper limb. Neuroanatomy 2009;8:15‐9. 9. Tong HC, Haig AJ, Yamakawa K. The Spurling test and cervical radiculopathy. Spine 2002;27:156‐ 9. 10. Anekstein Y, Blecher R, Smorgick Y, Mirovsky Y. What is the best way to apply the Spurling test for cervical radiculopathy? Clinical orthopaedics and related research 2012;470:2566‐72. 11. Levin KH, Maggiano HJ, Wilbourn AJ. Cervical radiculopathies: comparison of surgical and EMG localization of single‐root lesions. Neurology 1996;46:1022‐5. 12. Date ES, Kim BJ, Yoon JS, Park BK. Cervical paraspinal spontaneous activity in asymptomatic subjects. Muscle & nerve 2006;34:361‐4. 13. Upton AR, McComas AJ. The double crush in nerve entrapment syndromes. Lancet 1973;2:359‐ 62. 14. Osterman AL. The double crush syndrome. The Orthopedic clinics of North America 1988;19:147‐55. 15. Kwon HK, Hwang M, Yoon DW. Frequency and severity of carpal tunnel syndrome according to level of cervical radiculopathy: double crush syndrome? Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology 2006;117:1256‐9. 16. Boden SD, McCowin PR, Davis DO, Dina TS, Mark AS, Wiesel S. Abnormal magnetic‐resonance scans of the cervical spine in asymptomatic subjects. A prospective investigation. The Journal of bone and joint surgery American volume 1990;72:1178‐84. 17. Eskander MS, Drew JM, Aubin ME, et al. Vertebral artery anatomy: a review of two hundred fifty magnetic resonance imaging scans. Spine 2010;35:2035‐40. 18. Song KJ, Choi BW, Kim GH, Kim JR. Clinical usefulness of CT‐myelogram comparing with the MRI in degenerative cervical spinal disorders: is CTM still useful for primary diagnostic tool? Journal of spinal disorders & techniques 2009;22:353‐7. 19. Buchowski JM, Liu G, Bunmaprasert T, Rose PS, Riew KD. Anterior cervical fusion assessment: surgical exploration versus radiographic evaluation. Spine 2008;33:1185‐91. 20. Olivero WC, Dulebohn SC. Results of halter cervical traction for the treatment of cervical radiculopathy: retrospective review of 81 patients. Neurosurgical focus 2002;12:ECP1.
Figure Legend Figure 1: Brachial Plexus – Source/Permissions Pending Figure 2: Lateral radiograph of a of a 64 year old gentleman who developed C8 radiculopathy due to adjacent segement pathology at C7/T1. Notice the low lying manubrium, which would allow for an anterior approach to C7/T1 without an osteotomy. Figure 3A: Parasagittal computed tomography (CT) scan the aforementioned gentleman with adjacent segment pathology. Notice the foraminal stenosis at C7/T1 due to disc osteophyte formation and facet hypertrophy. Figure 3B: Axial CT scan showing severe right and moderate left foraminal stenosis due to ventral osteophytes and facet hypertrophy. Figure 4: Axial magnetic resonance imaging scan of a 69 year old woman who developed a C8 radiculopathy in the absence of radiographic compression. She was successfully managed with a fusion, immobilizing the segment.
Fig 2
Fig 3A
Fig 3B
Fig 4
Myeloradiculopathy: C8 And T1 Radiculopathy Michael P. Kelly MD, Lindley B. Wall MD, Geoffrey E. Stoker BS, K. Daniel Riew MD
www.elsevier.com/locate/enganabound
PII: DOI: Reference:
S1040-7383(14)00024-0 http://dx.doi.org/10.1053/j.semss.2014.05.008 YSSPS480
To appear in: Seminars in Spine Surgery
Cite this article as: Michael P. Kelly MD, Lindley B. Wall MD, Geoffrey E. Stoker BS, K. Daniel Riew MD, Myeloradiculopathy: C8 And T1 Radiculopathy, Seminars in Spine Surgery, http://dx.doi.org/10.1053/j.semss.2014.05.008 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Myeloradiculopathy: C8 And T1 Radiculopathy Michael P. Kelly, MD1, Lindley B. Wall, MD1, Geoffrey E. Stoker, BS2, K. Daniel Riew, MD1 1
Washington University School of Medicine, Department of Orthopedic Surgery, Saint Louis, MO
2
Washington University School of Medicine, Saint Louis, MO
From Washington University School of Medicine, Department of Orthopedic Surgery No funding support. Reprint requests Michael P. Kelly, MD Department of Orthopedic Surgery IOH 5th Floor, Box 8233 660 South Euclid Avenue Saint Louis, MO 63110 Abstract Objective: To review the diagnosis and treatment of C8 and T1 radiculopathies. Findings: Due rarity and to overlap in sensory and motor contributions, diagnosis of C8 and T1 radiculopathies may be difficult. This may also be due, in part, to an incomplete knowledge and understanding of the brachial plexus and peripheral nerve anatomy. The C8 and T1 nerves provide sensory innervation proximal to the wrist, which is important when distinguishing between these radiculopathies and an ulnar compressive lesion. Conclusions: Understanding plexus anatomy will allow surgeons to distinguish between C8 and T1 radiculopathies, with particular attention to other pathologies which present with similar complaints.
Introduction Cervical spondylosis or herniated nucleus pulposus causing radiculopathy or myeloradiculopathy is among the most common pathologies treated in a spine surgery clinic. The most commonly affected levels are C5‐C6, C6‐C7, and C4‐C5, respectively1 Far less common is C7‐T1 and T1‐T2 pathology, causing a C8 or T1 radiculopathy, with a prevalence of 6.2% of affected nerve roots in one series.1 Cervical pathologies causing these radiculopathies include herniated nucleus pulposus and cervical spondylosis. Less common causes of C8/T1 radiculopathy include tumors, for example Pancoast tumors.2 Additionally, a small number of patients may present with no evidence of spinal pathology at C7‐T1.3 When evaluating patients with upper extremity pain, one must exclude other potential pathologies such as shoulder or peripheral compressive neuropathies. With particular respect to C8 radiculopathy, compressive lesions of the ulnar nerve, such as cubital tunnel or Guyon’s canal syndrome, may cause similar presenting complaints and symptoms. This is an important point to emphasize, as spine surgeons have been shown to have difficulty differentiating between ulnar nerve pathologies and pure C8 pathologies.4 The purpose of the paper presented here is to review C8 anatomy and the diagnosis and management of C8/T1 radiculopathy. Anatomy The brachial plexus is comprised of the ventral rami of the 5th cervical nerve root through the 1st thoracic nerve root and is formed by the 13th week of gestation. In some cases, contribution from the 4th cervical root may create a “prefixed” brachial plexus or, conversely, the 2nd thoracic root may contribute to the plexus, creating a “postfixed” brachial plexus.5‐7BRACHIAL PLEXUS IMAGE(Figure 1) In these cases, the additional root contribution may be the cause of discrepancies between radiographic pathologies and dermatomal symptoms. The 8th cervical root terminates in the median nerve, the ulnar nerve, the medial brachial cutaneous and the medial antebrachial cutaneous nerves. Understanding the dermatomes and myotomes related to these three terminal branches and C8 is essential to making the proper diagnosis. A survey of spine surgeons has shown that a thorough knowledge and understanding of this anatomy is uncommon.4
C8
C8 exits the cervical spine between the C7 and T1 vertebra, providing branches to the median nerve, the ulnar nerve and the medial antebrachial nerve. As such, there may be confusion regarding which nerve is affected. C8 provides sensory innervation to the medial arm, medial (ulnar) forearm, and the ring and small fingers. Neither the median nerve nor the ulnar nerve provide sensory innervation proximal to the wrist, a key point when discriminating a C8 radiculopathy from a peripheral compressive neuropathy, like cubital tunnel syndrome.
C8 provides some motor innervation to nearly all muscles of the hand and forearm. Of particular note are the abductor pollicis brevis, superficial head of the flexor pollicis brevis, opponens pollicis, and the lateral lumbricals. These intrinsic muscles of the hand receive C8 innervation, provided by the median nerve and not the ulnar nerve. This distinction is important when one is evaluating a C8 radiculopathy versus an ulnar compressive lesion. The abductor pollicis brevis is responsible for the majority of opposition and is tested by instructing the patient to raise the thumb 90 degrees to the plane of the palm. The flexor pollicis brevis is responsible for flexion of the proximal phalanx of the thumb. Opponens pollicis abducts and flexes the first metacarpal and is tested by instructing the patient to touch the tip of the thumb to the small finger. The lumbricals are responsible for, and tested by, flexion of the metacarpophalangeal joints while maintaining extension at the interphalangeal joints.
T1
The T1 nerve root exits between the first and second thoracic vertebra and also provides branches to the median, ulnar, brachial cutaneous and antebrachial cutaneous nerves. As previously noted, neither the median nor the ulnar nerve provide sensory innervation proximal to the forearm. Again, this point is important when discriminating between a cervical pathology and some peripheral, compressive pathology. The sensory disturbance associated with a T1 radiculopathy may affect the axilla, while this is uncommon with a C8 radiculopathy. The motor weakness associated with a T1 radiculopathy may be most profoundly observed in weakness of the abductor digiti minimi. The overlap between C8 motor innervation and T1 motor innervation may make the diagnosis difficult, however. Sympathetic innervation to the face comes from T1, and not C8, and a Horner’s syndrome (ptosis, meiosis, anhydrosis) may be seen with these lesions and this may be the most telling symptom of T1 pathology.
Ulnar Nerve
A peripheral compressive neuropathy of the ulnar nerve may be confused with a C8 radiculopathy. The ulnar nerve provides sensory innervation to the ulnar border of the hand, the small finger, and the ulnar half of the ring finger. There is no ulnar contribution to the sensory innervation proximal to the wrist. The dorsal ulnar aspect of the hand receives innervation from the dorsal sensory branch of the ulnar nerve, which originates proximal to the wrist. Thus, a palmar sensory disturbance is concerning for a distal compression at Guyon’s canal. A sensory disturbance to the palmar and dorsal ulnar border of the hand and small finger suggests a compression of the ulnar nerve proximal to the branching of the dorsal sensory branch at the cubital tunnel. However, ulnar nerve compression will not cause a sensory disturbance in the forearm or arm. The ulnar nerve innervates the majority of the intrinsic muscles of the hand, though does not provide innervation to the abductor pollicis brevis, superficial head of the flexor pollicis brevis, opponens pollicis, nor the lateral lumbricals as previously mentioned. Knowing this will allow surgeons to distinguish ulnar nerve pathology from C8 pathology. An exception to this may occur in cases of Marinacci communications, where a forearm ulnar nerve to median nerve pathway exists; other similar, though rare, anatomic variations are the Riche‐Cannieu anastomosis (deep ulnar to recurrent median) and the Berretini anastomosis (communications between
common digital nerves).8 Common areas of ulnar nerve compression include the cubital tunnel and Guyon’s canal.
Median Nerve
The median nerve supplies innervation to the remainder of the hand: specifically sensation to the palmar and dorsal thumb, index, long and radial ring fingers. Median nerve pathology will not cause a sensory deficit in the forearm, as this is innervated by the lateral antebrachial cutaneous nerve, a branch of the musculocutaneous nerve. In addition to innervating the muscles of the volar forearm, the median nerve innervates the abductor pollicis brevis, superficial head of the flexor pollicis brevis, opponens pollicis, and the lateral lumbricals. There are a number of areas where pathologic compression of the median nerve may occur, though the carpal tunnel is the most common. Diagnosis Physical Examination As with any examination, a complete and thorough history should be taken. This will provide the surgeon with information that may suggest pathologies aside from C8 radiculopathy or a peripheral compressive neuropathy, such as diabetic neuropathy or a rheumatologic diagnosis. Inciting events as well as pain modifying activities should be sought. The Spurling maneuver may be useful when diagnosing a cervical radiculopathy.9 Extension of the neck and lateral bending to the ipsilateral side of the pain may create concordant pain, while flexion and lateral bending to the contralateral side will provide relief.10 The Spurling maneuver is useful to help determine those patients that are candidates for a laminoforaminotomy, rather than some other procedure. If the Spurling maneuver is not positive, particularly if there is no relief with flexion, then enlarging the foramen via laminoforaminotomy is unlikely to provide significant benefit to the patient. The shoulder abduction test is performed by abducting the affected limb past 90 degrees.This maneuver relaxes the tension on the brachial plexus and thus can relieve pain. Specific commonly used provocative tests performed in the arm include the Tinel’s test and Phalen’s test. The Tinel’s is performed by percussing along the course of the affected nerve (median or ulnar) to elicit paresthesias in the dermatome of the nerve. Phalen’s compression test is performed by instructing the patient to hold both hands and fingers in flexion, to increase carpal tunnel pressure and provoke signs of a median neuropathy. Inspection of the hand should examine for wasting of the thenar, hypothenar, and lumbrical musculature. Isolated thenar wasting may suggest a median nerve lesion, while isolated hypothenar wasting may suggest an ulnar nerve lesion. Mixed wasting may suggest a C8 lesion, including profound wasting of the intrinsics as seen in myelopathy hand. Myelopathy hand is rarely seen without pathology cranial to C6‐C7, however. Signs and symptoms of myelopathy, including ataxia, hyperreflexia, and pathologic reflexes should be investigated, as a C8 radiculopathy may exist in the setting of a myeloradiculopathy. Electrodiagnostic Studies
Electrodiagnostic studies may be useful in determining pure radiculopathy, pure peripheral neuropathy, and mixed, so‐called “double crush”, pathologies. These studies are also useful in determining other symptomatic spinal levels, which may be contributing to the symptoms, such as C7 or T1. Electromyography studies (EMG) are particularly useful when evaluating a radiculopathy, as they can help localize motor changes to a single level. The muscle groups consistently associated with a C8 radiculopathy, are the first dorsal interosseous, abductor digit minimi, abductor pollicis brevis, flexor pollicis longus, and extensor indicis proprius.11 When an EMG is performed, the paraspinal musculature should be examined as well. The paraspinals receive motor innervation from the ipsilateral dorsal rami of the exiting root. These fibers can be compressed only at the foramen and not in a peripheral neuropathy, though asymptomatic patients can have EMG changes in the cervical paraspinals.12 Nerve conduction studies (NCS) are used to evaluate for evidence of demyelinating disease or sensory conduction abnormalities, as may be seen in cubital tunnel syndrome. A cervical radiculopathy should not have abnormal NCS in the absence of a peripheral lesion. NCS will also help determine the presence of a “double crush” pattern, where there is a concomitant compression at the cervical level and at a distal site.13 Concomitant disease has been reported in approximately 10‐20% of patients.14,15 In both EMG and NCS, clinical suspicion should drive the diagnosis, as false positives and negatives are common.(AAEM, Muscle Nerve 1999) Imaging The radiographic evaluation of a C8 radiculopathy should include plain radiographs, with anteroposterior, lateral, and oblique images. The C7‐T1 level may be difficult to visualize, depending on the position of the sternum and the shoulders, though one should look for evidence of degenerative disease, particularly foraminal stenosis due to bone spurs and/or hypertrophy of the superior facet of T1. One should notice the level of the manubrium relative to the cervical spine when planning an anterior approach for management of a C8 radiculopathy.(Figure 2) In rare cases, access to the C7‐T1 disc may be difficult. Flexion and extension lateral radiographs will allow for evaluation of instability at the C7‐T1 segment and will give some information about the rigidity of the segments cranial to C7‐T1. In the authors’ experience, C8 radiculopathies may exist at segments without severe radiographic disease if they are below rigid lever arms, either severe spondylosis or a cervical fusion. Magnetic resonance imaging (MRI) is useful for evaluation of nerve root compression, particularly those caused by disc herniations. As with electrodiagnostics, clinical suspicion should drive the diagnosis, as asymptomatic changes are common on MRI.16 Not to be neglected on the MRI is the anatomy of the vertebral artery. Whether approaching the cervical spine from an anterior or posterior approach, the surgeon must always know the anatomy of the vertebral artery. While most will enter the cervical spine at C6 (92%), a small number will enter the foramen transversarium at C7 (0.6%).17 Computed tomography scanning is useful to evaluate bony anatomy, including the facet joints, as hypertrophy of either joint will contribute to foraminal stenosis.(Figures 3A,B) As with the lateral radiograph, the mid‐sagittal CT cut can provide information about the extent of distal exposure that is possible without an osteotomy of the manubrium. A CT myelogram provides useful information
regarding neural compression, but is more invasive than an MRI and is used when MRI is contraindicated.18 When evaluating areas of compression, one must remember that a nerve root may be affected by a large paracentral disc herniation at the segment cranial to its exit, particularly in a pre‐ fixed brachial plexus.3 Thus, a large C6‐C7 disc herniation may cause a C8 radiculopathy. Similarly, in a post‐fixed brachial plexus, pathology at the T1‐T2 level, affecting the T1 nerve root, may cause symptoms consistent with a C8 radiculopathy. CT Scanning is useful, though not perfect, for evaluating the success of prior fusion procedures, as pseudarthrosis may not be detected on plain films and may be the cause of a radiculopathy.19 Hehir et al. have published a series of 31 patients with C8 radiculopathy, as confirmed by EMG. They found that nerve root compression at the C7‐T1 level was inconsistent, observed in only 16% of patients. Compression at the C7 nerve root was observed in 16% of patients and at the T1 nerve root in 3% of patients. These findings suggest that a pre‐fixed or post‐fixed brachial plexus may present with C8 radiculopathy in the absence of C7‐T1 pathology. Nearly one third of the patients in this series had no specific findings. This mirrors our experience in a number of patients with C8 radiculopathy in the absence of radiographic compression. (Figure 4) Management
Nonoperative
The natural history of cervical radiculopathies, particularly those due to a herniated nucleus pulposus, has not been studied as thoroughly as lumbar disease. Nonetheless, non‐operative management for 6‐8 weeks should be considered the minimum prior to surgical intervention; the majority of patients will improve within 3 months and thus avoid surgery.1 Therefore, in the absence of incapacitating pain refractory to non‐operative interventions, such as epidural steroid injections, progressive neurologic deficits, or static motor or sensory deficits that would be deemed troublesome by the patient should they become permanent, we recommend non‐operative treatment for at least 3 months. If there is constant numbness that would bother the patient if it became permanent or profound weakness (grade 2/5), we offer surgery to decompress the affected root as quickly as possible, to prevent permanent damage. We also recommend early surgery if there is weakness of the intrinsic hand muscles due to C8‐T1 radiculopathy, as these typically take longer to improve than more proximately innervated muscles. Transforaminal epidural steroid injections are useful and are used for both therapeutic and diagnostic purposes. As noted previously, radiographic abnormalities are common and a multitude of pathologies may produce distal arm pain, so pain relief from a C8 nerve root block is confirmatory of radiculopathy and provides valuable data to the treating surgeon. Other nonoperative treatments may include physical therapy and cervical traction exercises. These interventions have not been well studied and their effectiveness is unknown, though short term results appear good.20
Operative
In our experience, operative management of C8/T1 radiculopathies is no different from other cervical radiculopathy. We reserve laminoforaminotomies for those patients with a primary complaint of arm pain, no evidence of segmental instability (including kyphosis), and a positive Spurling maneuver. As
noted before, the latter is the primary driver of indicating laminoforaminotomies in our practice. The remaining patients may be treated with anterior or posterior decompression and fusion procedures (e.g. anterior cervical discectomy and fusion) or with cervical total disc arthroplasty. Conclusion C8 and T1 Radiculopathies are uncommon and this may account for some of the difficulty observed in the diagnosis and management of this pathology. A careful physical examination will often reveal C8 radiculopathy, ulnar compressive neuropathies, and “double crush” syndromes. Surgeons must know the different presentations of these pathologies. An ulnar neuropathy will not affect the forearm sensory examination, while a C8 radiculopathy may. A T1 radiculopathy may cause sensory deficits as high as the axilla, which would be uncommon with a C8 lesion. Similarly, no thenar musculature receives innervation from the ulnar nerve, so examination of the LOAF (Lateral Lumbricals, Opponens pollicis, Abductor pollicis brevis, superficial head of Flexor pollicis brevis) is mandatory and will help distinguish C8 pathology from ulnar nerve pathology. A T1 pathology may manifest with profound intrinsic weakness, particularly with the abductor digiti minimi. The radiographic findings may be obvious or nonexistent. We have diagnosed and treated, successfully, patients with C8 radiculopathy in the absence of radiographic findings. Often these patients have a rigid lever arm above the C7‐T1 segment. Electrodiagnostics may offer some valuable information, but the history and physical examination must drive the diagnosis. Selective nerve root blocks or transforaminal epidural steroid injections may be both therapeutic and diagnostic. A small sampling of spine surgeons showed knowledge gaps regarding the myotomes and dermatomes associated with the C8/T1 nerve root and the ulnar nerve. Any surgeon treating arm pain, whether radiculopathy or neuropathy, should know and understand the commonalities and differences. Radiographic studies and electrodiagnostics may support a diagnosis, but in a small number of cases the diagnosis is made by the history and physical examination. Once the diagnosis of C8/T1 radiculopathy is made, management is consistent with other cervical radiculopathies.
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Figure Legend Figure 1: Brachial Plexus – Source/Permissions Pending Figure 2: Lateral radiograph of a of a 64 year old gentleman who developed C8 radiculopathy due to adjacent segement pathology at C7/T1. Notice the low lying manubrium, which would allow for an anterior approach to C7/T1 without an osteotomy. Figure 3A: Parasagittal computed tomography (CT) scan the aforementioned gentleman with adjacent segment pathology. Notice the foraminal stenosis at C7/T1 due to disc osteophyte formation and facet hypertrophy. Figure 3B: Axial CT scan showing severe right and moderate left foraminal stenosis due to ventral osteophytes and facet hypertrophy. Figure 4: Axial magnetic resonance imaging scan of a 69 year old woman who developed a C8 radiculopathy in the absence of radiographic compression. She was successfully managed with a fusion, immobilizing the segment.
Fig 2
Fig 3A
Fig 3B
Fig 4