What causes hyperexcitability?
Dysfunction of voltage-gated K+ channels in peripheral axons causes hyperexcitability that manifests as cramps, myokymia and fasciculation in Isaacs’ syndrome. 1 Because axonal hyperexcitability itself is neurotoxic in experimental animals,2 Isaacs’ syndrome might also cause secondary axon loss.
What is peripheral hyperexcitability?
Peripheral nerve hyperexcitability (PNH) is a syndrome of spontaneous and continuous muscle fiber activity, cramps, and slow relaxation of muscles of peripheral nerve origin. 1,2. The electrophysiologic basis consists of spontaneous bursts of single motor unit discharges with a high intraburst frequency.
How is peripheral nerve hyperexcitability treated?
The management of primary PNH syndromes comprises symptomatic treatment with anticonvulsant drugs, immune modulation if necessary, and treatment of possible associated dysimmune and/or malignant conditions.
What is muscle hyperexcitability?
Peripheral nerve hyperexcitability (PNH) is the term used to describe a group of disorders characterized clinically by muscle cramps, muscle twitching (fasciculations or myokymia), muscle stiffness, and pseudomyotonia (delayed muscle relaxation after contraction).
What is hyperexcitability of the nervous system?
Central hyperexcitability refers to an increased responsiveness of nociceptive neurons in the central nervous system to their normal or subthreshold afferent input (i.e., central sensitization) [7].
What causes nerve excitability?
Nerve excitability is principally determined by the state of membrane sodium channels, which can be influenced by factors such as drugs or the ionic composition of the extracellular fluids.
What is muscle excitability?
Excitability is the ability to respond to a stimulus, which may be delivered from a motor neuron or a hormone. Extensibility is the ability of a muscle to be stretched or extended.
Which is the best description of peripheral nerve hyperexcitability?
Peripheral nerve hyperexcitability (PNH) syndromes can be subclassified as primary and secondary. The main primary PNH syndromes are neuromyotonia, cramp-fasciculation syndrome (CFS), and Morvan’s syndrome, which cause widespread symptoms and signs without the association of an evident peripheral nerve disease.
How is split hand determined by nerve excitability?
Methods In 35 patients with genetically confirmed SBMA, 55 with ALS, 158 with other neuromuscular diseases and 90 normal controls; split hand was strictly determined by amplitudes of compound muscle action potentials. Nerve excitability testing of median motor axons was performed in 35 SBMA and 55 patients with ALS and 45 normal controls.
What is the index of Split hand excitability?
Split hand index = (APB CMAP amplitude × FDI CMAP amplitude)/ADM CMAP amplitude. Multiple nerve excitability measurements were performed in the median nerve at the wrist, using a computerised programme (Institute of Neurology, London, UK).
What is the split hand sign in ALS?
Objective The ‘split hand’ sign refers to preferential wasting of the thenar and first dorsal interosseous muscles with relatively sparing of the hypothenar muscles in amyotrophic lateral sclerosis (ALS) and both cortical and spinal/peripheral excitotoxic mechanisms have been proposed.