History
Mr. Tsang was a 70-year-old gentleman. He is an ex-smoker and regular drinker.
He has a past medical history of hypertension, hyperlipidemia, gout, and bilateral glaucoma. He did not have a family history of gait disturbance or muscle atrophy.
He presented with a longstanding history of recurrent falls since 2-3 years ago, the frequency of which has increased in the recent 1 year. The falls were usually due to tripping over the tip of his toes as they tend to scrape the ground while walking. He had to adapt by raising his leg higher to clear the ground.
He also reported sequential limb weakness for 1 year, beginning in the right lower limb, followed by the left lower limb, right upper limb, and lastly the left upper limb.
He had experienced significant weight loss and thinning of his muscles in the involved limbs.
Choking on his saliva had been an increasingly frequent occurrence.
There were no ocular, bulbar, or sphincter symptoms.
Physical examination
Cranial nerves were normal. There was no tongue wasting.
Neck power was full. The upper limbs displayed asymmetrical proximal weakness while the lower limbs demonstrated asymmetrical distal weakness.
Fasciculations were noted over the right triceps and bilateral quadriceps.
Tone was normal. Reflexes were mixed with upper limb hyporeflexia and lower limb hypereflexia. Ankle clonus was absent.
There was no ataxia or sensory level.
A gait examination was pertinent for a high-steppage gait.
Investigations
A nerve conduction test revealed asymmetrical axonopathy of the bilateral medial, ulnar, and peroneal nerves. The lower limbs were disproportionately affected compared to the upper limbs. The sensory responses were relatively preserved.
Electromyography suggested chronic neuropathic changes with active denervation over 3 segments.
An MRI of the cervical cord was unremarkable.
Thought process
The pathology was likely localized to the anterior horn cell, given the mixed upper and lower motor neuron signs with bulbar involvement.
Provided the longstanding history, neurodegenerative, genetic, and metabolic etiologies were considered to be at the top of the differential diagnoses.
In particular, motor neuron disease was the working diagnosis.
Next steps
Riluzole was initiated. He was referred to a multidisciplinary team for comprehensive non-pharmacological care.
Clinical and electrophysiological monitoring was required to review the clinical diagnosis.