Muscle and Neuromuscular Treatments: Restoring Excitability and Contractile Knobs

Muscle and neuromuscular treatments restore the excitability and contractile knobs the disease perturbs: pyridostigmine restores the myasthenic safety factor, amifampridine raises Lambert-Eaton quantal content, mexiletine normalises channelopathy excitability, steroids and gene therapy slow muscular dystrophy, resistance training partially reverses sarcopenia, and eccentric loading rebuilds tendinopathy.

Each muscle or neuromuscular treatment moves the cited knob back toward normal. Myasthenia gravis restores the post-synaptic safety factor so the RNS decrement falls below the 10% diagnostic threshold; Lambert-Eaton raises presynaptic quantal content; channelopathies return the depolarization-block threshold from both excitability signs. Muscular-dystrophy therapy is disease-modifying (lower damage rate, raise dystrophin, shifting Duchenne toward Becker) and sarcopenia training is partial — it stays below young values because the ageing floor remains [O].

Muscle and neuromuscular: restoring excitability and contractile knobs

This group perturbs the shared FitzHugh-Nagumo membrane and the muscle contractile contact number; each treatment restores the specific knob its disease moved. The table summarises; the blocks give the mirror action and the real drug or load.

Treatment by disease

Myasthenia gravis

Treatment: pyridostigmine (acetylcholinesterase inhibitor) + immunotherapy (steroids / rituximab / thymectomy). mechanism §10

Kernel action (mirror): restore the post-synaptic safety factor (lower theta) so low-frequency NMJ depression no longer drops recruitment. How the real intervention acts: AChE inhibition raises synaptic ACh and re-clears the end-plate threshold; immunotherapy removes the AChR block at source

Grade: decrement abolished as the safety factor is restored [V]; AChEi target + 10% diagnostic threshold [L]; absolute strength gain [O]

Lambert-Eaton myasthenic syndrome (LEMS)

Treatment: amifampridine (3,4-diaminopyridine); treat underlying SCLC where paraneoplastic. mechanism §10

Kernel action (mirror): raise presynaptic quantal content (baseline release) back toward normal. How the real intervention acts: K-channel block widens the presynaptic action potential, increasing Ca influx and ACh quantal content, which restores baseline NMJ efficacy

Grade: baseline transmission restored as quantal content rises [V]; 3,4-DAP target [L]; absolute strength gain [O]

Channelopathies: myotonia & periodic paralysis

Treatment: mexiletine (Na-channel blocker, myotonia); acetazolamide / potassium management (periodic paralysis). mechanism §15

Kernel action (mirror): return the membrane recovery parameter (depolarization-block threshold) toward normal from BOTH excitability signs. How the real intervention acts: Na-channel block damps the myotonic hyperexcitability; carbonic-anhydrase inhibition / serum-K control corrects the depolarization-block-prone state

Grade: both excitability signs returned to the normal block threshold [V]; mexiletine / acetazolamide targets [L]; absolute attack frequency [O]

Muscular dystrophy (Duchenne / Becker)

Treatment: corticosteroids (deflazacort / prednisone) + exon-skipping / micro-dystrophin gene therapy. mechanism §14

Kernel action (mirror): (a) lower the per-contraction damage scale A; (b) raise the dystrophin fraction so fragility (1 - dystrophin) falls -- shifting a DMD trajectory toward Becker. How the real intervention acts: steroids stabilise the sarcolemma and slow contraction-induced tearing; restoring partial dystrophin reconnects the contractile lattice to the membrane / ECM, lowering per-cycle damage

Grade: DISEASE-MODIFYING: lowering A slows loss and raising dystrophin shifts DMD → BMD trajectory [V]; reading-frame restoration + steroid evidence [L]; cure / absolute timeline [O]

Sarcopenia

Treatment: progressive resistance training + adequate dietary protein (+ vitamin D where deficient). mechanism §14

Kernel action (mirror): raise the recruitment and fibre-size axes back up (partial); the fatigue axis improves too. How the real intervention acts: resistance training drives motor-unit recruitment and type-II fibre hypertrophy, partially reversing two of the three decline axes; protein supplies the synthetic substrate

Grade: PARTIAL reversal: training raises max force but stays below young [V]; resistance-training evidence (Fiatarone) [L]; absolute strength / ageing floor [O]

Tendinopathy

Treatment: eccentric / heavy-slow resistance loading (mechanotransduction) + load management. mechanism §17

Kernel action (mirror): deload below the fatigue threshold (arrest further loss) + controlled load drives collagen re-deposition (partial contact re-cross). How the real intervention acts: the loading PARADOX: uncontrolled overuse tears contacts, but controlled high-load slow eccentric work is the mechanotransductive stimulus for collagen synthesis and remodelling

Grade: deloading arrests progression [V]; eccentric-loading rebuild is mechanistic, absolute collagen regeneration [O]; Alfredson eccentric-loading protocol [L]

Disease-modifying, not curative — stated plainly

Muscular-dystrophy therapy is disease-modifying. Corticosteroids lower the per-contraction damage scale and partial dystrophin restoration reconnects the contractile lattice, shifting a Duchenne trajectory toward Becker; neither is a cure, and the absolute timeline stays open.

Sarcopenia training is partial. Resistance training reclaims part of the lost recruitment and fibre-size axes but stays below young values: the ageing floor remains. Tendinopathy deloading arrests further loss, and eccentric loading is the mechanotransductive rebuild, but the absolute regenerated collagen fraction is open.