4. Signs of MND:
A. Head and Neck:
MND expresses itself in the head and neck region in the form of facial weakness, depressed gag reflex, weak palatal movements, tongue fasciculations and depressed jaw jerk.
If there is exaggerated gag reflex, brisk jaw jerk and stiff tongue and palate, then it is pseudobulbar palsy.
Expression of MND in the limbs can be in 2 forms either upper motor neuron signs or lower motor neuron signs or mixed pattern. Upper motor neuron pattern consists of weakness, spasticity, hyperreflexia and positive Babinski’s sign.
While lower motor neuron type pattern includes weakness, flaccidity, atrophy, hyporeflexia and fasciculations.
All the investigations to rule out other conditions causing weakness and wasting such as myopathies, neuropathies, neuromuscular junction disorders, myelopathy etc should be carried out.
After exclusion of all other differentials MND can be diagnosed with nerve conduction study and electromyography where there will be normal motor and sensory nerve conduction studies (some reduction in compound muscle action potential amplitude and area in case of extreme wasting). Electromyography will show denervation and reinnervation potentials on electromyography in the form of giant, polyphasic motor unit action potenials with discrete interference pattern. These changes will be in myotomal pattern that is all muscles of the same myotome will depict similar features on electromyography.
6. Differential Diagnosis:
Following are the important conditions that should be differentiated from MND:
A. Cervical Myelopathy Secondary to Spondylosis:
cervical myelopathy resulting from cervical spondylosis, develops slowly and gradually. It leads to wasting of intrinsic muscles of hands and causes spastic paresis.
B. Multifocal Motor Neuropathy (MMN):
MMN mimics MND closely hence it should be differentiated explicitly. It expresses as lower motor neuron signs only and is associated with anti-GM1 ganglioside antibodies.
C. Kennedy’s Disease:
Also known as X-liked bulbospinal neuropathy, it expresses as perioral fasciculations and lower motor neuron signs.
Other features include gynaecomastia, testicular atrophy and diabetes mellitus. It is also associated with CAG expansion in androgen androgen receptor locus.
D. Benign Fasciculations:
Following conditions are associated with benign fasciculations hence these should be excluded meticulously before diagnosing MND. These conditions include Tay-sachs disease, hyperthyroidism and lymphoproliferative disorders.
Mainly its management constitutes supportive treatment because there is no significant option for specific treatment.
A. Supportive Treatment:
Supportive treatment is provided as and when required during the course of the treatment. Supportive treatment options include wheel chair for mobility, ventilatory support for respiration, percutaneous endoscopic gastrostomy tube placement for feeding after impairment of swallowing, anticholinergics or tricyclics for saliva reduction to control sialorrhoea, communication devices to compensate for lost speech and many other options for specific problems as they arise.
B. Specific Treatment:
Riluzole can be given, which is a sodium channel blocker hence inhibits the glutamate release. It however arrests the disease progression very minimally and complete blood counts and liver function tests should be monitored when it is being administered.