What can go wrong with the wiring — and which failure counts in minutes?
Nervous system disease splits by mechanism into families the page teaches in order of urgency: the vascular blackout (stroke — the emergency where minutes of saved time equal saved brain), the peripheral dying-back (neuropathy — most commonly diabetic, the glove-and-stocking burning the diabetes page's complication story), the insulation attacked (MS), the dopamine generator failing (Parkinson's), the storm (epilepsy — synchronized misfiring), and the tuning disorders (anxiety and depression — by far the most common conditions of this system, our dedicated pages' territory). The field's unifying rule: neurological symptoms are time-sensitive until proven otherwise — the FAST stroke rules and the ascending-weakness emergency exist because the wiring forgives delay least.
The blackout: a clot or bleed cutting blood flow to brain tissue — 1.9 million neurons die per minute of large-vessel occlusion. The FAST signs are the public-health invention that saves brains; thrombolysis and thrombectomy (Chapter 5's story) are the treatment windows. The prevention tier: blood pressure, glucose, smoking, atrial fibrillation — the modifiable ledger of our hypertension and diabetes pages, read from the wiring end.
The dying-back: the longest nerves failing first — diabetes the leading cause (50% of diabetics over time), then B12 deficiency, alcohol, thyroid disease, and the chemotherapy class. The glove-and-stocking burning, the numb feet that ulcerate because pain is the protector they lost. The workup-first rule: the three mimics (glucose, B12, thyroid) before any shelf. Chapter 4's ALA adjunct lives here.
The insulation attacked: the immune system stripping CNS myelin at scattered plaques — optic neuritis, numbness, weakness, fatigue in relapses and remissions. The treatment transformation is among neurology's greatest: from nothing to a dozen disease-modifying immunotherapies in a generation. Diagnosis-speed matters; the earlier the therapy, the better the trajectory.
The dopamine generator failing: the substantia nigra's cells lost, the movement system losing its smoothing signal — tremor, rigidity, slowness, the masked face. Levodopa remains the transformational therapy (1967); deep-brain stimulation refines the advanced disease. The gut's constipation often precedes the tremor by years — the enteric link this page teaches.
The storm: populations of neurons synchronizing into runaway discharges — seizures of every presentation from the classic convulsion to the two-minute absence. One in twenty-six people will have a seizure in their lifetime; the anticonvulsant tier controls most. First-ever seizure = emergency evaluation; the driving rules and the seizure-action plan are the safety tier.
The tuning disorders: the network's alarm and reward chemistry mis-tuned — the most common nervous system conditions by an order of magnitude, and this estate's most-visited pages. The tier: CBT and the SSRI/SNRI prescription classes (genuinely effective, stigmatized far beyond their reality), with the shelf as adjunct at best. Our anxiety and depression pages carry both in full.
Nervous system prevention is vascular prevention, metabolic discipline, and three safety rules: