What ALS is and how it presents
ALS is the most common form of motor neuron disease, characterised by progressive degeneration of both upper motor neurons (in the brain) and lower motor neurons (in the spinal cord). This produces a combination of upper motor neuron signs (spasticity, hyperreflexia, Babinski sign) and lower motor neuron signs (muscle weakness, atrophy, fasciculations). The disease typically begins focally � often in one limb or bulbar muscles � and spreads progressively.
Common presentations include limb-onset ALS (weakness, atrophy, fasciculations in hand or leg muscles) and bulbar-onset ALS (difficulty speaking, swallowing, or chewing). Respiratory muscle involvement occurs later and is the most common cause of mortality. The diagnosis is primarily clinical, supported by electromyography (EMG) showing widespread denervation, and by excluding mimics such as cervical spondylotic myelopathy, multifocal motor neuropathy, and Kennedy disease.
- Progressive muscle weakness and atrophy
- Fasciculations (muscle twitching)
- Spasticity and hyperreflexia
- Difficulty speaking or swallowing (bulbar involvement)
- Respiratory muscle weakness in advanced disease
Related: Neurologist Kathmandu → · Dr. Jitendra Knowledge Hub → · ICHD-3 Topic →
Diagnostic evaluation and mimics
ALS diagnosis requires evidence of both upper and lower motor neuron dysfunction in multiple body regions, progressive spread over time, and exclusion of other conditions that could mimic ALS. EMG/nerve conduction studies are essential to demonstrate widespread denervation and exclude focal neuropathies. MRI of brain and cervical spine excludes structural mimics such as spondylotic myelopathy or multiple sclerosis.
Important mimics to exclude include cervical spondylotic myelopathy (compressive myelopathy treatable surgically), multifocal motor neuropathy with conduction block (treatable with immunotherapy), inclusion body myositis, and Kennedy disease (X-linked spinal and bulbar muscular atrophy). Blood tests may include creatine kinase, thyroid function, and genetic testing when hereditary motor neuron disease is suspected. Dr. Jitendra Prasad Yadav (NMC 8029) provides structured evaluation at Kathmandu Neurology Clinic, Durbar Marg, Opposite of Yak & Yeti Hotel.
| Test | Purpose | Finding in ALS |
|---|---|---|
| EMG/NCS | Denervation pattern | Widespread lower motor neuron involvement |
| MRI brain/cervical spine | Exclude structural mimics | Normal or non-specific changes |
| Blood tests | Exclude metabolic causes | Normal or non-specific |
| Genetic testing | Hereditary forms | SOD1, C9orf72 mutations in some cases |