Anatomical etiology of “pseudo-sciatica” from superior cluneal nerve entrapment: a laboratory investigation

Figures & data

Figure 1 Photograph and the corresponding illustration showing five branches of the SCN on the left side of a specimen obtained from the cadaver of a 90-year-old woman (specimen no. 8). The most lateral branch (a5) had separate origins from the T12 and L2 nerve roots. The third most medial branch (a3) had separate origins from the L2 and L3 nerve roots.

Abbreviation: SCN, superior cluneal nerve.

Figure 2 Photographs and the corresponding illustration showing three branches of the SCN on the right side of a cadaveric specimen obtained from an 89-year-old man (specimen no. 22). The L5 nerve roots had a dorsal branch ramifying into the most medial SCN branch (a1) and the second most medial branch (a2). The lateral branch of the SCN (a3) had separate origins from the L2 and L3 nerve roots.

Abbreviation: SCN, superior cluneal nerve.

Table 1 Levels of lumbar nerve root originating SCN branches

Specimen number	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23
T12								☆												▽			□
L1				□	□	☆	☆	▽		☆					□		□						△
L2	▽	□		△		□▽	▽	□☆	□	▽	▽	▽		□	△	□	○	□	□	□	□	□
L3	□		□	○	△	▲	■	□	△	△		□	□	△	○	△	○	△	△	△		□
L4	△	△	△		○	●	●△	▲	○	□	□	△	△	○		○	○△	○	○	○	△		●
L5	○	○	○					●		●	●△	○	○								●	○△

Notes:

○ : The most medial branch.

△ : The second most medial branch.

□ : The third most medial branch.

▽ : The fourth most medial branch.

☆ : The most lateral branch.

Under bar (_): represents branch passing through osteofibrous passing through tunnel.

Black marks represent branch with possible entrapment.

Black symbols represent entrapped branches within the osteofibrous tunnel.

Figure 3 Photographs showing entrapped branches of the medial branch of the SCN in cadaveric specimen no. 23. a2 is the second most medial branch of SCN.

Abbreviation: SCN, superior cluneal nerve.

Table 2 Distances from anatomical landmarks and diameter of superior cluneal nerves

Specimen number	Distance from midline (mean ± SD), mm	Distance from PSIS (mean ± SD), mm	Diameter of SCN (mean ± SD), mm
T12	91.5±4.8	66.0±13.4	1.5±1.0
L1	90.1±14.5	60.6±16.5	1.3±0.6
L2	78.8±13.4	50.7±9.9	1.5±0.4
L3	71.5±13.9	42.9±11.4	1.5±0.3
L4	66.7±13.9	42.6±10.1	1.6±0.6
L5	62.4±22.2	40.8±18.1	1.8±0.5

Abbreviations: SCN, superior cluneal nerve; PSIS, posterior superior iliac spine.