Multiple Sclerosis
Autoimmune demyelination of CNS; separated in time and space; optic neuritis, internuclear ophthalmoplegia (MLF lesion), oligoclonal bands in CSF.
Parkinson Disease
Degeneration of substantia nigra pars compacta (dopamine loss); TRAP triad (Tremor at rest, Rigidity, Akinesia/bradykinesia, Postural instability); Lewy bodies (alpha-synuclein).
Huntington Disease
Autosomal dominant CAG trinucleotide repeat on chromosome 4; caudate atrophy; chorea, dementia, depression; anticipated in paternal transmission.
Myasthenia Gravis vs. LEMS
MG: autoantibodies against post-synaptic AChR; weakness WORSENS with muscle use; thymoma association. LEMS: anti-P/Q presynaptic Ca2+ channels; weakness IMPROVES with use; SCLC association.
Neuromuscular Junction Disorders: MG vs. Lambert-Eaton
| Feature | Myasthenia Gravis (MG) | Lambert-Eaton Myasthenic Syndrome (LEMS) |
|---|---|---|
| Antibody Target | Post-synaptic Nicotinic acetylcholine receptors (AChR) (85%) or MuSK | Presynaptic voltage-gated P/Q-type calcium channels (VGCC) |
| Muscle Use Response | Weakness fatigues and WORSENS with repetitive muscle use | Weakness IMPROVES with repetitive muscle exertion |
| Ocular & Bulbar Involvement | Prominent: Ptosis and diplopia (early), dysphagia, dysarthria | Spares ocular muscles; proximal lower extremity pelvic girdle weakness predominates |
| Autonomic Symptoms & Reflexes | Normal deep tendon reflexes; no autonomic dysfunction | Depressed/absent deep tendon reflexes; autonomic dysfunction (dry mouth, erectile dysfunction) |
| Malignancy Association | Thymoma (15%) or thymic follicular hyperplasia (75%); chest CT mandatory | Small Cell Lung Cancer (SCLC) (60%); paraneoplastic neuroendocrine origin |
| Medical Therapy | Pyridostigmine (AChE inhibitor) ± Thymectomy ± Prednisone; Plasmapheresis/IVIG in crisis | Amifampridine (3,4-DAP) or Pyridostigmine; treat underlying Small Cell Lung Carcinoma |
Movement Disorders: Parkinson vs. Huntington vs. Essential Tremor
| Disorder | Neuropathology & Genetics | Tremor & Motor Profile | First-Line Therapy |
|---|---|---|---|
| Parkinson Disease | Loss of dopaminergic neurons in substantia nigra pars compacta; intracellular Lewy bodies containing alpha-synuclein | Resting 'pill-rolling' tremor (4–6 Hz), cogwheel rigidity, masked facies, festinating gait; improves with voluntary movement | Levodopa-Carbidopa (most effective); Dopamine agonists (Pramipexole); MAO-B inhibitors (Selegiline) |
| Essential Tremor | Autosomal dominant familial predisposition in 50%; exacerbated by stress and caffeine | Action / Intention tremor (worsens with sustained posture or goal-directed movement); temporarily relieved by alcohol | Propranolol (non-selective beta-blocker) OR Primidone (anticonvulsant); deep brain stimulation of VIM thalamus |
| Huntington Disease | Autosomal dominant CAG trinucleotide repeat expansion in HTT gene on chromosome 4; anticipation; caudate and putamen atrophy | Chorea (involuntary, irregular, dance-like jerks), motor impersistence, grimacing, progressive cognitive decline and psychosis | Tetrabenazine or Deutetrabenazine (VMAT2 inhibitors to deplete dopamine); atypical antipsychotics for psychosis |
OMM Board Correlate: Postural Instability & Hypertonicity
- Rigidity and Axial Mechanics: Parkinsonian cogwheel rigidity leads to severe thoracic kyphosis, forward head carriage, and restriction in rib cage excursion. Articulatory and gentle myofascial techniques improve vital capacity and balance.
- Avoid Rapid Cervical HVLA: In elderly patients with Parkinsonism or neurodegenerative disorders, aggressive high-velocity thrusts are contraindicated due to cervical spondylosis and impaired protective autonomic reflexes.
Board Traps & Common Distractors
- Guillain-Barré Syndrome (GBS) presents with symmetric ascending flaccid paralysis following a gastrointestinal (Campylobacter jejuni) or respiratory infection; monitored with Serial Forced Vital Capacity (FVC) and Negative Inspiratory Force (NIF); FVC < 20 mL/kg mandates elective endotracheal intubation.
- In Myasthenia Gravis, avoid medications that exacerbate neuromuscular transmission failure, including Aminoglycosides, Fluoroquinolones, Beta-blockers, and Magnesium.
- Internuclear Ophthalmoplegia (INO) in a young adult is strongly indicative of Multiple Sclerosis; lesion resides in the Medial Longitudinal Fasciculus (MLF): on lateral gaze, the ipsilateral adducting eye cannot cross midline, and the contralateral abducting eye displays monocular horizontal nystagmus.