Acronym for myoclonus epilepsy with ragged-red fibers.
Belongs to a group of rare muscular disorders called mitochondrial encephalomyopathies. The most
characteristic symptom is myoclonic seizures that are usually sudden, brief,
jerking spasms that can affect the limbs or the entire body. Ataxia, lactic
acidosis, dysarthria, optic atrophy, short stature, hearing loss, dementia,
and nystagmus may occur.
Mitochondrial; incidence of affected children
is dependent upon maternal mutant load.
Defect of the respiratory chain enzymes, mainly
complexes I and IV.
Clinical and laboratory confirmation of elevated
pyruvate and lactate. Muscular biopsy shows ragged-red muscle fibers, and
the biochemical defect is often segmental on histochemistry.
Clinical spectrum is proportional to the amount
of normal and mutant DNA. Onset is in the neonatal period, with mental
deterioration, intention tremor, myoclonic epilepsy, spasticity, ataxia,
muscle weakness and atrophy, myopathy, and sensory neural hearing loss. The
neuropathologic findings are (a) degeneration of dentate nucleus, red
nucleus, globus pallidus, subthalamic nucleus, and pontine tegmentum; (b)
degeneration of the Clarke column (the dorsal nucleus of the spinal cord), spinocerebellar tract, posterior column
and corticospinal tract, and posterior spinal nerve root and sural nerve;
and (c) degeneration of substantia nigra, locus caeruleus, cerebellar
cortex, and inferior olivary nucleus.
Diagnosis of mitochondrial disease
should be considered in any child with a multisystem neurologic disorder or
who is being investigated for hypotonia. Anesthesia-related morbidity and
mortality risk is essentially linked to the preoperative status of the
child, that is, the number and extent of organ dysfunction. The presence of
a mitochondrial disease is not considered a risk for malignant hyperthermia.
Avoid any elective anesthesia/surgery in the presence of infection or
temperature because cytokines (mainly tumor necrosis factor (TNF)), inhibit some complex of the
respiratory chain. The following should be checked: central nervous system (seizures, myoclonus,
strokes, swallowing problems); metabolic (usual venous or arterial concentration of
lactates and glucose); muscles (hypotonia, contractures, scoliosis); cardiac (even if the
child is asymptomatic, ECG and echocardiography to exclude conduction
disorders and cardiomyopathy, respectively; check functioning of pacemaker,
if present); pulmonary (frequent infections, chronic aspiration, pulse oximetry
breathing room air, obstructive and/or central apnea; reduced ventilatory
drive is common, and many patients have an abnormal response to both hypoxia
and hypercarbia, and deaths have been reported following sedation with
chloral hydrate or diazepam); hepatic and renal dysfunctions; nutritional status and diet (glucose and/or lipid
rich; tolerance to fasting and treatment [carnitine, vitamin Q,
Usual treatment until the morning of
surgery. Preoperative fasting as short as possible; if fasting is usually
poorly tolerated, a glucose-containing solution should be started when
fasting period starts. A sedative premedication is best avoided because of
the possible abnormal response to hypoxia/hypercarbia. Induction: No contraindication
to choice of anesthetic; however, the dosage of sedative agents might
require reduction; sevoflurane is the best choice for inhalation induction;