Table 7.

Impact of CAG expansion on cortical and hippocampal volumes. This table illustrates the impact of CAG triplet expansion on the volumes of various cortical areas, including the frontal, insular, occipital, parietal, and temporal cortices, as well as the hippocampus, in individuals at risk of developing Huntington’s disease. The participants are categorized based on the number of CAG repeats: ≤26 (normal), 27–35 (intermediate), and ≥40 (full penetrance).

Structures	Substructures	CAG	N	Average Range	Mean	Standard Deviation	Minimum	Maximum	Kruskal–Wallis H Test	p
Cortical areas	Frontal cortex	≤26	28	17.66	136.736	16.6920	99.5	178.0	3.484	0.175
		27–35	2	32.00
		≥40	6	17.92
	Left frontal cortex	≤26	28	17.79	68.853	8.4647	50.2	88.8	3.228	0.199
		27–35	2	31.50
		≥40	6	17.50
	Right frontal cortex	≤26	28	17.48	68.164	8.3325	49.3	89.3	4.327	0.115
		27–35	2	33.50
		≥40	6	18.25
	Insular cortex	≤26	28	18.04	11.1517	1.45717	8.42	14.50	1.222	0.543
		27–35	2	26.50
		≥40	6	18.00
	Left insular cortex	≤26	28	18.11	5.5375	0.75031	4.11	7.17	1.572	0.456
		27–35	2	27.50
		≥40	6	17.33
	Right insular cortex	≤26	28	17.73	5.6142	0.71584	4.30	7.35	1.481	0.477
		27–35	2	27.00
		≥40	6	19.25
	Occipital cortex	≤26	28	17.07	48.203	4.6208	34.8	59.3	2.981	0.225
		27–35	2	28.75
		≥40	6	21.75
	Left occipital cortex	≤26	28	17.52	23.686	2.3424	17.3	28.2	1.982	0.371
		27–35	2	28.00
		≥40	6	19.92
	Right occipital cortex	≤26	28	16.75	24.511	2.5215	17.5	31.1	4.534	0.104
		27–35	2	31.25
		≥40	6	22.42
	Parietal cortex	≤26	28	18.41	124.433	11.9950	95.6	152.0	4.523	0.104
		27–35	2	32.50
		≥40	6	14.25
	Left parietal cortex	≤26	28	18.36	61.4975	5.90719	48.00	76.20	4.085	0.130
		27–35	2	32.00
		≥40	6	14.67
	Right parietal cortex	≤26	28	18.39	62.892	6.2177	47.7	76.2	5.154	0.076
		27–35	2	33.50
		≥40	6	14.00
	Temporal cortex	≤26	28	17.63	108.156	13.1853	84.8	137.0	3.244	0.197
		27–35	2	31.50
		≥40	6	18.25
	Left temporal cortex	≤26	28	17.46	55.164	6.6123	43.5	69.9	3.330	0.189
		27–35	2	31.50
		≥40	6	19.00
	Right temporal cortex	≤26	28	17.61	52.906	6.6293	41.3	66.9	3.248	0.197
		27–35	2	31.50
		≥40	6	18.33
	Left hippocampus	≤26	28	17.23	4.1364	0.27691	3.58	4.69	1.897	0.387
		27–35	2	21.25
		≥40	6	23.50
	Right hippocampus	≤26	28	18.00	4.2328	0.29162	3.74	4.88	0.622	0.733
		27–35	2	16.50
		≥40	6	21.50

Note: For the analysis of brain volumes and triplet expansion, the following statistical tests were used: Kolmogorov–Smirnov method, Student’s t-test, two-way analysis of variance with Bonferroni post hoc test, and Spearman’s test. The p values show no statistically significant differences. Source: own elaboration.