B. Facial onset sensory and motor neuronopathy
Evidence of motor dysfunction in multiple cranial nerves, marked distal muscle weakness and atrophy, and significant neurogenic lesions on muscle biopsy indicate axonal damage of multiple nerves or lesions of motor nuclei of the brainstem and spinal anterior horn. Meanwhile, facial sensory disturbance and the absence of the blink reflex suggests trigeminal nerve involvement. Juvenile and insidious onset and unrelenting gradual disease progression are indicative of genetic, degenerative, and metabolic diseases.
Lesions with sensory and motor neuron involvement, including syringomyelia and syringobulbia, Sjögren syndrome, vasculitis, certain metabolic disorders, and immune-mediated peripheral neuropathy were precluded by negative laboratory, neuroimaging, and neurophysiological results. The normal lipid profile excluded Tangier disease, a rare autosomal recessive disorder with variants in the ATP-binding cassette transporter 1 gene (ABC1), characterized by reduced high-density lipoprotein and apolipoprotein A through I.1 Multiple axonal sensorimotor neuropathy, in conjunction with pyramidal signs, may be linked to Charcot-Marie-Tooth neuropathy type 2 with KIF5A, GDAP1, SPG11, MFN2, and GJB1 variants2; however, facial and trigeminal nerve involvement is rare. The involvement of upper and lower motor neurons may be linked to amyotrophic lateral sclerosis (ALS); however, clinical symptoms related to sensory involvement and the absence of the blink reflex could not be explained by an ALS diagnosis.