To describe the clinical and electrodiagnostic characteristics of 8 patients with bilateral lower lumbosacral radiculopathies who were found to have conus medullaris lesions on neuroimaging.

Conus medullaris syndrome is typically due to extradural compression of the distal spinal cord from disc herniation at the T12-L2 levels. It presents with progressive, disabling, lower extremity weakness, sensory loss, pain, and sphincter dysfunction. Diagnosis is typically made with imaging and electrodiagnostic studies. However, we have noticed a discrepancy between electrodiagnostic findings, which may show only lower lumbosacral root disease, while neuroimaging shows conus compression from thoracic or high lumbar disc herniation. This discrepancy can lead to diagnostic confusion and delay treatment. A similar discrepancy has been reported in patients with upper lumbar stenosis (see Park et al, Muscle and Nerve 2020; 61(5):580-586).

This is a case series of 8 patients seen in the last year in our EMG Laboratory who were found to have conus medullaris compression on MRI spine or CT myelography.

Of the 8 patients, radicular back pain was present in 50% (n=4), bilateral in 75% (n=3). Muscle weakness was present in all patients: 62.5% (n=5) in L5 and 37.5% (n=3) in the S1 distribution. Sensory loss was present in 87.5% (n=7): 75% (n=6) in L5 and 12.5% (n=1) in the S1 distribution. 25% (n=2) had absent knee reflexes. No patients had absent ankle reflexes or sphincter disturbance. Electrodiagnostic examination localized the lesion to the bilateral L5 roots in 37.5% (n=3), bilateral S1 roots in 12.5% (n=1), and bilateral L5 and S1 roots in 50% (n=4).

Bilateral lower lumbosacral radiculopathy can masquerade as conus medullaris syndrome, which can be missed on lumbosacral imaging that does not include the conus. In such cases, the provider must be sure to request that the conus be included on diagnostic neuroimaging.