Cervical lower motor neuron syndromes: A diagnostic challenge.

Cervical lower motor neuron (LMN) syndromes, also known as brachial paresis, are characterized by muscle atrophy, weakness, and decreased reflexes in the upper limbs, devoid of sensory symptoms. These syndromes can stem from various factors, including degenerative conditions, immune-mediated diseases, infections, toxic exposures, metabolic disorders, and vascular anomalies. Clinical presentations vary, with motor neuron involvement potentially limited to the cervical area or extending to other regions, affecting prognosis. Misdiagnosis is a significant issue, particularly in lower motor neuron presentations, with an error rate nearing 20 %. This review proposes a classification system based on magnetic resonance imaging (MRI) findings, the onset timing of symptoms (acute, subacute, or chronic), the symmetry and distribution of atrophy, and the etiology (sporadic or hereditary). Acute conditions may include spinal ischemia, whereas subacute or chronic forms can manifest as symmetric (e.g., cervical spondylogenic myelopathy) or asymmetric (e.g., Hirayama disease) presentations. Neurophysiological assessments and cervical MRI are crucial for accurate diagnosis, as they reveal patterns that provide lesion localization and additional clues to the underlying cause. A systematic diagnostic approach is essential for navigating the complexities of these syndromes.