A 70-year-old man reported a 2-year history of numbness on the left side of his face. Over time, complaints of speech disorder and difficulty in chewing were added. Then within 6 months, slowly progressive weakness of the left-hand distal muscle appeared to attend global atrophy of the left upper limb muscles. Due to progressive distal weakness of the left upper limb, the patient began to drop objects and could not raise his arm above head level. Soon after, he had weakness in his left leg and difficulty walking. Then the patient was admitted to the neurology department of our hospital. Neurologic examination revealed weakness in bilateral masseter muscles, more prominent on the left, and decreased sensation of touch, temperature, pain in all three branches of the trigeminal nerve and absent corneal reflexes on the left side. Speech was dysarthric, palatal and pharyngeal reflexes were absent. Atrophy and fasciculations were observed on the tongue. Light touch on the limbs, vibration, and proprioception were intact. Strength testing revealed weakness in the neck flexors, left arm, and proximal leg muscles. Muscle stretch reflexes and coordination were normal.
In nerve conduction study (NCS), by Natus Medical Incorporated, Pleasanton, USA, sensory nerve action potential (SNAP) amplitude could not be obtained in the left median, ulnar, and sural nerves. SNAP amplitude is low in the right median, ulnar, and sural nerves. Compound muscle action potential (CMAP) amplitudes of the left ulnar, peroneal, and bilateral tibial nerves are small, conduction velocity is normal, and conduction block is not observed. The bilateral median nerve, right ulnar nerve, and peroneal nerve are normal. The latency of the bilateral tibial F response is prolonged. Fibrillation, PKD and fasciculations were observed in the tongue, bilateral lower and upper limb muscles. Motor unit potential (MUP) loss, prolonged duration, and high amplitude of MUPs were noted. It has been observed that the interference pattern decreases.
The blink reflex abnormalities were characterized by prolonged R1 and R2 responses. Importantly, abnormal blink reflexes were observed in the context of normal facial nerve CMAP responses, suggesting dysfunction in the afferent limb of the blink reflex pathway.
The patient was diagnosed with facial-onset sensory and motor neuronopathy syndrome (FOSMN), a rare variant of motor neuron disease (MND).
The patient was planned for differential diagnosis, but the patient left because he lived in France. When the patient was called for control 7 months later, we learned that the patient died. The investigations of the patient made in France were revised, Anti-acetylcholine receptor antibodies were negative. The results of the cerebrospinal fluid analysis were normal. Lyme, HIV, syphilis serology were negative. Vasculitis and tumor markers were negative. The ganglioside panel (anti-GM1 and Gd1b) was positive. Magnetic resonance imaging (MRI) of the cervical spine was normal. There was mild diffuse cortical atrophy on cranial MRI. There was no significant finding in the left deltoid muscle biopsy. In the left sural nerve biopsy, there were findings consistent with the Wallerian degeneration of the nerve. Repetitive nerve stimulation (RNS) from the nasal muscle was normal.
The patient, whose ganglioside panel was also positive, was given intravenous immunoglobulins at a dose of 2 g/kg in the autoimmune pathology hypothesis and riluzole 100 mg/day was started. The patient partially benefited from the treatment. But 7 months later, his condition worsened, dysphagia required percutaneous endoscopic gastrostomy (PEG) tube placement, and the patient died after pneumonia.