Table 1.

Proportion of Subjects by Group Who Responded Affirmatively to a Structured Medical History Questionnaire

	Percentage (Mean [SD])
Symptom	Patients With MELAS	Carrier Relatives	Controls	P Valuea
Headache	91	58	52	<.001b,c
Balance difficulty	81	20	4	<.001b,c
Age at onset of migraines, y	77 (19.3 [10.0])	32 (21.9 [12.3])	16 (21.3 [10.4])	<.001b,d
Limb weakness	71	22	4	<.001b,c,d
Age at onset of clumsiness, y	62 (19 [14])	23 (37 [17])	4	<.001b,c,d
Age at onset of myoclonus, y	50 (24 [17])	15 (33 [15])	0	<.001b,c,d
Loss of sensation	48	19	4	<.001b,d

Abbreviation: MELAS, mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (syndrome).

^aThe χ² test was used to evaluate the heterogeneity across the 3 groups.

^bSignificant difference between patients and carrier relatives.

^cSignificant difference between carrier relatives and controls.

^dSignificant difference between patients and controls.