Table III.

Confirmatory tests for organ dysfunction in mitochondrial myopathy.

Symptom/sign/disorder	Tests	Possible abnormalities	Examples of treatments
Seizures, encephalopathy	EEG	Epileptiform abnormality, diffuse slowing	Anticonvulsants
Stroke-like episodes	MRI brain	High-signal T2 abnormality not conforming to vascular territories, posterior-predominant	L-arginine a possible therapy
Sensory neuropathy	Nerve conduction studies	Axonal sensory or sensorimotor neuropathy	Symptomatic therapy
Myopathy	CK	Normal or slightly elevated. May be very high in CoQ10 deficiency
EMG	Myopathic changes or normal
Respiratory failure	PFTs, sleep studies	Decreased FVC. Apnoeic episodes during sleep	CPAP or BiPAP
Cardiac	Electrocardiogram	Conduction abnormalities	Antiarrhythmics, pacemaker
	Echocardiogram	Cardiomyopathy	ACE inhibitors
Endocrinopathy	Fasting glucose, glucose tolerance test, HgBA1c, TSH, calcium, PTH, cortisol, synacthen test	Abnormalities consistent with type 2 diabetes mellitus, and/or hypothyroidism, and/or hypoparathyroidism, and/or adrenal failure	Oral antihyperglycaemic agents and/or insulin; L-thyroxine; hydrocortisone
Cognitive dysfunction	Mental status testing	May indicate cognitive impairment
Hearing loss	Audiography	Sensorineural-type hearing loss	Auditory aids, cochlear implantation
Ocular symptoms/signs	Ophthalmology referral	Oculomotor abnormalities, optic atrophy, pigmentary retinopathy	Corrective lenses, surgery for strabismus or ptosis
Dysphagia	Swallowing studies (video fluoroscopy or manometry)	Cricopharyngeal achalasia or oesophagealdysmotility	Dietary modification
Other general tests	Serum lactate	Normal, or elevated
	CSF lactate	Normal, or elevated
	CSF analysis	Normal, or elevated protein
	CT brain	Normal, or basal ganglia calcifications ± atrophy
	MRI brain	Basal ganglia signal abnormalities, non-specific white matter abnormalities, stroke-like lesions, cerebellar or brain-stem atrophy, or normal. MR spectroscopy may demonstrate elevated lactate