Hypoconnectivity of the Amygdala in Patients with Low-Back-Related Leg Pain Linked to Individual Mechanical Pain Sensitivity: A Resting-State Functional MRI Study

Figures & data

Table 1 Demographic Data and Clinical Characteristics of the LBLP and HC Groups

Characteristics	LBLP (n=35)	HC (n = 30)	P values
Demographic data
Age (y) Median (p25, p75)^a	53.0 (38.0, 60.0)	40.0 (38.0, 50.8)	0.076
Sex (M/F)^b	25/10	16/14	0.132
Duration of disease (months) Median (p25, p75)	3.00 (1.00, 12.00)	n/a	n/a
Clinical data
JOA	13.49±4.08	n/a	n/a
VAS	5.37±0.91	n/a	n/a
PRI	5.09±2.01	n/a	n/a
HAMD	4.29±2.30	n/a	n/a
HAMA	2.26±1.38	n/a	n/a
von Frey filament (vF) test values (mN) (p25, p75)
vF test of left hand (mN)	588.0 (255.0, 588.0)	n/a	n/a
vF test of right hand (mN)	588.0 (255.0, 588.0)	n/a	n/a
vF test of left lumbar (mN)	58.8 (39.2, 147.0)	n/a	n/a
vF test of right lumbar (mN)	58.8 (39.2, 98.0)	n/a	n/a
vF test of left calf (mN)	58.8 (78.4, 147.0)	n/a	n/a
vF test of right calf (mN)	58.8 (78.4, 98.0)	n/a	n/a
vF test of left foot (mN)	39.2 (58.8, 78.4)	n/a	n/a
vF test of right foot (mN)	39.2 (58.8, 78.4)	n/a	n/a
Neuroimaging data (mN)
Frame displacement Median (p25, p75)	0.012 (0.008, 0.026)	0.029 (0.016, 0.029)	0.506^a

Notes: ^aMann‒Whitney Test; ^bChi-square tests.

Abbreviations: LBLP, low-back-related leg pain; HC, healthy control; y, years; M, male; F, female; JOA, Japanese Orthopaedic Association; VAS, visual analogue scale; PRI, pain rating index; HAMD, Hamilton Depression Scale; HAMA, Hamilton Anxiety Scale; n/a, not available; mN, millinewton.

Table 2 Brain Regions with Altered Amygdala Functional Connectivity of LBLP and LBLP Subgroups (Voxel-Level P < 0.01, GRF Correction at Cluster-Level P < 0.05)

Brain Regions	BA	Peak	Voxels	MNI Coordinates
				X	Y	Z
Altered connectivity of left amygdala (LBLP vs HC)
Right paracentral lobule (PCL)	5, 7	−3.963	169	9	−36	66
Altered connectivity of right amygdala (LBLP vs HC)
Bilateral anterior cingulum (ACC)	32	−4.657	211	−6	33	18
Right postcentral gyrus (PoCG)	1, 2, 3	−4.285	307	9	−48	60
Left postcentral gyrus (PoCG)	1, 2, 3	−4.803	251	−24	−27	66
Altered connectivity pattern in acute or chronic LBLP
Altered connectivity of left amygdala (aLBLP vs HC)
Right putamen		−4.583	252	30	−18	9
Right paracentral lobule (PCL)	6	−4.484	156	12	−33	6
Altered connectivity of right amygdala (aLBLP vs HC)
Right putamen		−5.209	370	36	−12	−3
Right posterior temporal lobe	37	−4.169	139	57	−66	−6
Altered connectivity of right amygdala (cLBLP vs HC)
Bilateral ACC	32	−5.276	195	−6	33	18
Left PoCG	1, 2, 3	−4.341	162	−24	−27	66

Abbreviations: LBLP, low-back-related leg pain; HC, healthy control; aLBLP, acute LBLP; cLBLP, chronic LBLP; BA, Brodmann’s area; MNI, Montreal Neurological Institute coordinate system.

Figure 1 Altered connectivity of the left (A) and right (B) amygdala in LBLP patients (voxel-level P < 0.01, GRF correction at cluster-level P < 0.05).

Abbreviations: LBLP, low-back-related leg pain; HC, healthy control; rsFC, resting-state functional connectivity; LH, left hemisphere; RH, right hemisphere. PCL_R, right paracentral lobule; Bil-ACC, bilateral anterior cingulum; PoCG_R, right postcentral gyrus; PoCG_L, left postcentral gyrus.

Figure 2 Altered pattern of amygdala rsFC in aLBLP and cLBLP patients (voxel-level P < 0.01, GRF correction at cluster-level P < 0.05).

Notes: The top row is the results of group analysis for left (A) and right (B) amygdala rsFC for aLBLP patients and HCs (voxel-level P < 0.01, GRF correction at cluster-level P < 0.05). The bottom row is the results of between-group analysis for the right amygdala rsFC for cLBLP patients and HCs (C) (voxel-level P < 0.01, GRF correction at cluster-level P < 0.05), and a sketch map of the altered connectivity pattern in aLBLP and cLBLP (D).

Abbreviations: LBLP, low-back-related leg pain; HC, healthy control; aLBLP, acute LBLP; cLBLP, chronic LBLP; Bil-ACC, bilateral anterior cingulum; PoCG, postcentral gyrus; PTL, posterior temporal lobe; Put, putamen; AMY, amygdala; vF, von Frey filament; rsFC, resting-state functional connectivity; LH, left hemisphere; RH, right hemisphere.

Figure 3 Spearman correlational analysis between decreased rsFC of left amygdala (A) and right amygdala (B) and lg-transformed vF test values (lg(vF)), or partial correlational analysis between decreased rsFC of right amygdala (B) and the PRI scores in LBLP patients.

Abbreviations: LBLP, low-back-related leg pain; AMY, amygdala; PCL, paracentral lobule; ACC, anterior cingulum; PoCG, postcentral gyrus, vF, von Frey filament; PRI, pain rating index.