1. Background
Low back pain (LBP) in children and young adults is most often attributed to muscle strain or overuse but can also occur with other spinal conditions such as inflammatory arthropathies, disc herniation, radiculopathy, spondylolysis and spinal deformities such as scoliosis.1 While LBP is less common in school age children, the prevalence increases with age and is similar to that of the adult population by age 18.2 In the young adult population, juvenile degenerative disc disease (JDDD) can account for persistent pain and radiculopathy and often occurs as a result of trauma or injury.3 It may be present at multiple spinal levels, causing disc space narrowing and has been associated with concurrent congenital spinal stenosis, making nerve root pathology such as radiculopathy more likely.3
Electrodiagnostic (EDX) testing and magnetic resonance imaging (MRI) are useful in determining the presence of underlying spinal and nerve root pathology.4-6 EDX testing, including needle electromyography (EMG) and nerve conduction studies (NCS), in addition to thorough subjective and objective examination, can facilitate understanding of the location and severity of the lesion, as well as likely prognosis.4-6 EDX testing has moderate sensitivity (49-86%) and high specificity (95%) for detecting lumbosacral radiculopathy.7 The results of EDX and MRI may also be used to identify possible treatment options, to include the need for surgical interventions.4-6
2. Case Presentation
Subjective
An 18-year-old male high school student was referred for EDX testing including NCS and needle EMG of bilateral lower extremities (BLE) and needle EMG testing of the bilateral lumbosacral paravertebral muscles (PVM) with a referring diagnosis of lumbosacral radiculopathy. The patient reported a history of intermittent, central LBP for five years that worsened about three months ago with increased LBP severity and development of symptoms in BLE (left > right lower extremity). He described pain in the left greater than right buttock and posterior thigh to the knees with intermittent numbness and tingling (N/T) in the plantar and dorsal aspects of bilateral feet and intermittent N/T in the left posterior thigh and leg. The patient noted weakness of the left knee, especially in flexion but denied other weakness in the left lower extremity (LLE) or right lower extremity (RLE). The patient had undergone an epidural steroid injection (ESI) at L4-L5 about two weeks prior to his EDX testing with no relief of symptoms in the lower back or legs. He denied current or previous history of injury or trauma to the lower back or legs or incontinence of bowel or bladder. In addition, the patient denied pain, N/T or weakness in bilateral upper extremities (BUE)
Review of Systems
The patient reported that his general medical health was good, and he was not being evaluated or treated by his primary care provider for any illness or medical problem. The patient denied diabetes, heavy metal exposure, thyroid disease, renal disease, or alcohol abuse. Otherwise, the review of systems was non-contributory for cardiovascular, pulmonary, gastrointestinal, genitourinary, or endocrine disease. The patient had no family history of neuromuscular disease.
The EDX testing, including NCS and needle EMG, was described for the patient, and the patient gave verbal and written consent for the EDX testing. The patient also gave verbal permission for the use of his case including EDX testing results for educational purposes including presentation and publication.
Physical Examination
The patient had a normal gait cycle without limp or apparent weakness in BLE and was not using any adaptive equipment for ambulation. In standing, the patient was able to perform normal toe walking (both single and double stance) and heel walking and was able to squat to 60° of knee flexion bilaterally without pain or weakness in BLE. Active mobility of BLE was normal including all hip, knee, ankle, forefoot, and toe motions. Mo-tor strength of BLE was determined to be normal (5/5) for the bilateral hip, knee, ankle, forefoot, toe and foot intrinsic muscles. Muscle strength reflexes (MSRs) of the bilateral ankle jerk (S1) and knee jerk (L2-L4) testing were present and equal (2/4). The Babinski and Chaddock pathological reflexes were absent in BLE. Sensory testing including light touch and pain (pin prick) was normal in BLE including assessment of all dermatomes (L1-S3) and peripheral nerves in BLE. The bilateral pedal and posterior tibial arterypulses were palpable and equal. Bilateral straight leg raise tests were performed in both sitting and supine positions. LBP was elicited only with testing the RLE in a seated po-sition. No LBP or radicular symptoms were produced with SLR testing in a seated or supine position for the LLE and in a supine position for the RLE.
Nerve Conduction Studies
The procedures for performing NCS have been previously described in detail.4-6 Nerve conduction studies of the bilateral deep fibular (motor and F wave), tibial (motor and F wave), superficial fibular (sensory), and sural (sensory) nerves were normal (Table 1).
Electromyography
The procedures for performing needle EMG have been previously described in detail.4-6 Abnormal EMG findings, as demonstrated by increased insertional activity and the presence of abnormal spontaneous electrical activity (fibrillation potentials and positive waves) at rest, was noted in the left fibularis longus, lateral gastrocnemius, long head of the biceps femoris and sacral PVM. Fibrillation potentials observed were a mixture of small and large amplitude (< 100 > μV) which is compatible with the presence of both acute and chronic denervation.4-6 There was normal motor unit morphology (shape, duration and amplitude) and recruitment and interference patterns when testing these muscles during minimal and maximal voluntary contraction. The other muscles tested in BLE and the right sacral PVM were normal on EMG examination (Table 2).
Conclusion (EDX Testing)
There is electrophysiological evidence on this exam of a left S1 radiculopathic process in the LLE and left sacral PVM. This neuropathic process affects the axonal components of the left anterior primary rami (S1 innervated muscles in the LLE) and posterior primary rami (sacral PVM at the S1 vertebral level) with a mixture of acute and chronic denervation in the left fibularis longus, lateral gastrocnemius, long head biceps femoris and sacral PVM. The presence of EMG abnormalities in multiple LLE muscles representative of the S1 myotome but innervated by different peripheral nerves suggested that the lesion was localized to the left S1 nerve root: fibularis longus (L5-S1), lateral gastrocnemius (S1-S2), long head biceps femoris (L5-S1-S2), and sacral PVM (S1). The presence of EMG abnormalities in the LLE (anterior primary rami) and left sacral PVM (posterior primary rami) suggest that both components of the left S1 spinal nerve are involved. The normal findings in the left tibialis anterior (L4-L5), extensor hallucis longus (L5-S1), and semitendinosus (L5-S1-S2) suggested that involvement of the L5 nerve root was less likely.
There was no electrophysiological evidence on this exam of a left L2-L5 radiculopa-thic process in the LLE, right L2-S2 radiculopathic process in the RLE or right sacral PVM or bilateral tibial, deep fibular, superficial fibular or sural mononeuropathy.
The patient tolerated the NCS well and the EMG study fairly well with some discom-fort on needle testing of the right lateral gastrocnemius and left sacral PVM. Post EDX testing, the patient had no pain in the right lateral gastrocnemius and left sacral PVM, and no pain in the other muscles tested in BLE and bilateral sacral PVM
Magnetic Resonance Imaging (MRI)
The patient had completed an MRI of the lumbar spine three weeks prior to EDX testing. The radiology report noted degenerative disc disease at the L4-L5 and L5-S1 levels with a broad-based central protrusion at the L4-L5 level causing mass effect upon the thecal sac, causing mild to moderate canal narrowing. In addition, an eccentric disc bulge was noted at the L5-S1 level impinging upon the right S1 nerve root and abutting JCEWM. 2023, 1. 10.55566/JCEWM-D-23-00001 the left S1 nerve root. The disc spaces were unremarkable and the spinal canal neural foramina are widely patent at the L1-L2, L2-L3, and L3-L4 levels.
3. Interventions
Lumbar Transforaminal Epidural Steroid Injection (ESI) Due to a lack of improvement with conservative care, the patient underwent an ESI at the left L4-L5 and L5-S1 levels approximately two months after the development of his BLE symptoms. At an office visit eight days later, the patient reported no change in his radicular pain and N/T in BLE or LBP. He rated his LBP 9/10 on a pain severity scale.
Surgical Intervention An L4-L5 and L5-S1 left sided minimally invasive discectomy with the use of the neuro-surgical microscope and fluoroscopy for visualization was performed four months after development of radicular symptoms. The orthopaedic spine surgeon stated “a hemila-minectomy at left L4-L5 and L5-S1 levels was performed with excellent decompression and removal of disk material and got the nerve roots completely freed up”. He also noted that “the patient had conjoined (bifid) nerve root at the L5-S1 level which may or may not have contributed to the fact that he had two disk herniations at such a young age of 18 years.”
4. Outcome/Follow-up
At the patient’s one-week post-operative office visit, the patient reported decreased LBP (5/10). He had a slight increase in pain and N/T in the LLE. The orthopaedic spine surgeon stated that the “LLE symptoms seem to be somewhat worse than pre-op symp-toms may be due to small hematoma at the surgical site.” The patient was directed to continue post-operative rehabilitation with physical therapy. Post-operative rehabilita-tion was initiated post-op day one and consisted of spine mobility exercises, core and BLE strengthening exercises, and walking as tolerated. General conditioning exercises including anaerobic and aerobic activities were initiated as tolerated four weeks post-op. At a post-operative office visit two months after surgery, the patient had further decreased LBP (2/10) and denied pain or N/T in BLE. He was again directed to continue physical therapy.
5. Discussion
This case study details the diagnostic evaluation and management of an 18-year-old high school student with a five-year history of central LBP with more recent progression of symptoms into the LLE greater than RLE. The patient had subjective symptoms consistent with a bilateral S1 radiculopathic process with LBP. However, the clinical findings on physical examination were unremarkable for motor or sensory deficits or changes in muscle stretch reflexes that would be expected with a bilateral or unilateral S1 radiculopathy. EDX testing, specifically needle EMG testing, for this patient demonstrated a left S1 radiculopathic process involving both the anterior and posterior primary rami. The MRI was consistent with the EDX results. Surgical intervention confirmed the presence of the lumbar degenerative disc disease and nerve root pathology, and a conjoined (bifid) nerve root was also identified at the L5-S1 level.
Conjoined or bifid nerve root describes an embryological anomaly that most commonly affects the L5 and S1 nerve roots.8-9 There are a number of different anatomical presentations, most commonly involving two adjacent nerve roots that arise from a broad area of the dura and are covered by a common root sleeve but then separate and exit through different vertebral foramen.8-9 Another anatomical variation involves two nerve roots exiting one vertebral foramen.9 Conjoined nerve roots may be more susceptible to injury in part due to their increased size compared to typical nerve roots, causing them to occupy a greater percentage of the foraminal space than would otherwise be expected.8-9 In addition, conjoined nerve roots have multiple attachment points to nearby structures, potentially reducing the amount of nerve root excursion available.8 Any adjacent steno-sis or compression may be more likely to result in nerve root symptoms and/or pathology in the presence of a conjoined nerve root.8 In addition, a conjoined nerve root may produce radicular symptoms even in the absence of significant disk pathology or steno-sis and may not be appreciated on lumbar imaging.9 In this patient, the presence of conjoined L5 and S1 nerve roots may have increased this patient’s susceptibility to radiculopathy at a relatively young age.
Lumbar degenerative disc disease is commonly thought of as a condition affecting older adults, but it can be present in adolescents and younger adults.3 Dimar et al performed a retrospective review of 1,877 patients less than 21 years old and with persistent low back pain who were referred to a spine specialty practice.3 Review of patient charts and MRIs found 76 patients with lumbar degenerative disc disease (DDD) on MRI (34 males; 42 females; mean age 17.1 years; range 11.5 – 21.0 years). Thirty-one of these patients had associated lumbar radiculopathy, and thirteen had multilevel concurrent spinal stenosis.3 While most patients in the study were successfully treated with non-operative treatments, four underwent surgical intervention for severe lumbar radiculopathy. Dimar’s retrospective study looked at a group of adolescents referred to a spine surgeon, likely representing more severe pathology and/or symptoms than are typically seen in this age group, and it demonstrates the potential for serious spinal pathology in younger people.
Prior to the EDX testing, a thorough history and physical examination must be completed to determine the presence and/or extent of neurologic involvement in patients with clinical signs and symptoms of lower motor neuron pathology such as lumbosacral radiculopathy. A thorough history and physical exam also provides a foundational guide for subsequent EDX testing.4-6 Myotomal weakness is considered one of the strongest predictors of nerve root pathology on EMG, but the presence of dermatomal pain is the most sensitive symptom predictor of electrodiagnostic abnormalities.10 The combination of dermatomal pain, myotomal weakness and change in reflexes has a 78% specificity for lumbar radiculopathy on EMG.10 In this patient, only dermatomal pain was present without motor weakness or reflex changes. The electrodiagnostic testing performed was an important tool for identifying neurological injury that could not be appreciated on clinical exam.
6. Learning Points
- The presence of a conjoined or bifid nerve root may increase a patient’s susceptibility to radiculopathy or radiculopathic symptoms even in the absence of significant spinal pathology.
- Lumbar disc degeneration and herniation with associated radiculopathy can be present in adolescents and young adults, particularly after injury, and requires a com-prehensive evaluation.
- A thorough history and physical examination must be completed to determine the presence and/or extent of neurologic involvement in patients with clinical signs and symptoms of lower motor neuron pathology such as lumbosacral radiculopathy and to provide a foundational guide for subsequent EDX testing.
- EDX testing (including NCS and needle EMG) is performed to confirm the findings of a thorough history and physical examination and may identify neurological injury associated with radiculopathy in patients without neurological deficit on clinical exam.
References
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2. MacDonald J, Stuart E, Rodenberg R. Musculoskeletal low back pain in school-aged children: A review. JAMA Pediatr. 2017 Mar 1;171(3):280-287.
3. Dimar JR, Glassman SD, Carreon LY. Juvenile degenerative disc disease: a report of 76 cases identified by magnetic resonance imaging. Spine J. May-Jun 2007;7(3):332-337.
4. Kimura J. Electodiagnosis in Diseases of Nerve and Muscle: Principles and Practice. 3rd edition. Philadelphia: Davis; 2013
5. Greathouse DG, Ernst G, Halle JS, Shaffer SW. Electrophysiological Testing (Nerve Conduction and Electromyo-graphic Studies) in Primary Care for the Physical Therapist (Examination and Triage), 3rd edition (Boissonnault W, ed), Elsevier Saunders: Philadelphia, PA, 2020.
6. Dumitru D, Amato AA, Zwarts M. Electrodiagnostic Medicine. 2nd edition. Philadelphia:Hanley & Belfus. 2001.
7. Dillingham TR, Annaswamy TM, Plastaras CT. Evaluation of persons with suspected lumbosacral and cervical radiculopathy: Electrodiagnostic assessment and implications for treatment and outcomes (Part I). Muscle Nerve. 2020 Oct;62(4):462-473.
8. Jokhi VH, Ponde SV, Sonawane C, Bansal SS, Chavhan A. Conjoint lumbosacral nerve root – A case study. J Orthop Case Reports. 2015 Oct-Dec; 5(4):14-16.
9. Böttcher J, Petrovitch A, Sörös P, Malich A, Hussein S, Kaiser WA. Conjoined lumbosacral nerve roots: current aspects of diagnosis. Eur Spine J. 2004 Mar;13(2):147-51.
10. Hassan A, Hameed B, Islam M, Khealani B, Khan M, Shafqat S. Clinical predictors of EMG-confirmed cervical and lumbosacral radiculopathy. Can J Neurol Sci. 2013 Mar;40(2):219-24.
Appendix: Table 1
Abbreviations: Amp, amplitude; Dist, distance; O, onset; P, peak; P-T, peak to trough; SFN, superficial fibular nerve; T, trough; Vel, velocity.
Appendix: Table 2
Abbreviations: Amp, amplitude; Dur, duration; Fibs, fibrillation potential; Incr, increased; Ins Act, insertion activity; Int Pat, interference pattern; MUP, motor unit potentials; Nml, normal; PPR, posterior primary rami; Parasp, paravertebral muscles; Poly, polyphasic potentials; PSW, positive sharp waves; Recrt, recruitment