Painful tonic spasms in multiple sclerosis Domenico A. Restivo U.O. di Neurologia, P.O. “Nuovo Garibaldi” Catania PTS: DEFINITIONS PTS are unilatral or bilateral, sterotyped, involuntary muscular Contractions lasting less than 2 min and that may manifest several times/day. PTS usually continues for weeks or months and then disappear. They can be triggered by touch, hyperventilation, emotions, movement and are seldom preceded by a somesthesic “aura”. They may start from the face, arm, or leg, and spread to the adjacent part of the body. They are more common in primary and secondary progressive forms Carenza di dati di prevalenza • Verosimilmente (Solaro et al., 2004) 6-11% •Si correlazione EDSS •Si correlazione durata malattia •No correlazione età Si correlazione EDSS, durata malattia ed età (Solaro et al.,2004) (Nurmikko et al., 2010) The spasms originate in the CNS from hyperactivity in the central motor fibres, caused by lesion in the internal capsule, cerebral peduncle, medulla, or spinal cord Maimone et al., Arch Neurol 1994; Restivo et al., 2003; Solaro et al., 2004 O’Connor et al., Pain 2008; Ephaptic spreading of abnormal transient electric discharges throughout demyelinated axons, in the spinal cord, brainstem, or hemispheric white matter (Maimone et al., 1991, Solaro et al., 2004; Restivo et al., 2003; 2011) PATHOPHYSIOLOGY Although no direct evidence exists, the typically spasmodic muscle contraction suggests ectopically generated high frequency discharges, due to Na channel activation. In the demyelinated part of a nerve fiber in which the internodal membrane is exposed, membrane impedance is diminished, and the action current generated in the adjacent nodal membrane is shunted. This is considered to depolarize the nodal membrane. During functional recovery a relatively small number of Na+ channels may appear in the demyelinated internodal membrane and restore conduction, which also facilitates propagation Weiner et al., Ann Neurol 1980 A conferma di ciò, un farmaco bloccante i canali al sodio come la lidocaina che agisce legandosi alla parte all’interno della membrana del canale, con una attivazione dipendente dallo stato del canale e con una maggiore affinità per cellule in cui il potenziale di membrana è depolarizzato (blocco Voltaggio -dipendente) e per cellule che scaricano ad alta frequenza (blocco frequenzadipendente), potrebbe inibire l’esordio ed il perpetrarsi di una scarica ectopica Sakurai et al. 1998 •Nocicettivo (Sveden et al., 2004) •Neuropatico (Bonica JJ 1991) •Misto (Truini et al., 2012) Truini et al., J Neurol 2012 Because e the simultaneous activation of adjacent motor units, as in muscle cramps, the spasmodic muscle contraction induces extreme vasculature compression., ischemia, eventually giving rise to nociceptive pain (ischemic muscle pain). As soon as the spasm ends, the blood flow returns to normal and pain quickly recedes. However, although patients with MS-associated PTS have a CNS lesion, the key question is whether the pain is generated primarily in the spasmodic muscles or in the CNS Rog et al. Neurology 2005 PTS: SEDI I PTS DI SOLITO TENDONO A DIFFONDERE A DISTRETTI VICINIORI SONO LOCALIZZATI SOLO AI MUSCOLI DEGLI ARTI E DEL TRONCO ? Pharyngeal painful tonic spasms: paroxysmal painful swallowing Restivo DA, Solaro C, Maimone D, Pavone A, Marchese-Ragona R. Ann Int Med 2011 Treatment • Carbamazepine (Shapiro et al., 1997) • Gabapentin (Solaro et al., 1999) • Lidocaine iv/mexiletine x os (Sakurai and Kanazawa, 1997) • • • • Phenytoin (Solaro et al., 2004) Acetazolamide ? (Sathi et al., 1992) Tiagabine (Solaro et al., 1997) Benzodiazepines (Shapiro et al., 1997) NO RCT STUDIES !!! Because Lidocaine blocks the voltage-gated Na+ channels In a voltage- and frequency-dependent manner., fibers mediating positive symptoms are preferentially blocked. Lidocaine almost completely abolished PTS Similar effects were obtained with oral mexiletine (300-400 mg/day), a derived of lidocaine, but a lesser extension Sakurai et al. 1998 Cannabinoids, theoretically effective in both neuropathic and nociceptive pain components are efficacious, and are more efficacious in PTS than the purely neuropathic pains in MS patients Treatment Solo un RCT: THC/cannabidiol (CBD) Livello A di evidenza Evaluation •Pain Intensity Score (4-point pain score: 0= no pain; 1= mild; 2= moderate; 3= severe) •Number of occurrences (diary) •Polymyographic recordings from painful muscles Muscular hyperactivity Transcranial direct current stimulation (t-DCS) VA S 10 8 real 6 s ham 4 2 0 T0 T1 T2 T3 Number of oc c urrenc e 18 16 14 12 10 8 6 4 2 0 real s ham T0 T1 T2 T3