Introduction to our lab's computational model of the human spinal cord. The model combines finite element analysis, neural circuitry simulation, and nerve fiber (axon) simulation.

1. Spinal Cord Map v1.0, slide 1. 5/29/2016. Copyright © 2010 Dr. Jeffrey E. Arle, Lahey Clinic. All rights reserved.
Jeffrey E. Arle1,2 MD PhD, Nicolae Iftimia3 BS, Longzhi Mei1 MS,
Jay L. Shils4 PhD, and Kristen W. Carlson1*
1Dept. of Neurosurgery, Beth Israel Deaconess Medical Center,
Boston, MA, USA
2Dept. of Neurosurgery, Harvard Medical School, Boston, MA, USA
3Tufts University School of Medicine, Boston, MA, USA
4Dept. of Anesthesiology, Rush Medical Center, Chicago, IL, USA
Principal Investigators
Jeffrey E. Arle
Jay L. Shils
Nick Iftimia Research
Longzhi Mei, Software
Kris Carlson*, Computational Modeling and Simulation
*Corresponding author: kwcarlso@bidmc.harvard.edu
The Human Spine Connectome
Part 1: Calculation of spinal cord segment volume, neurons/segment, and
neurons/Rexed lamina

3. WHITE MATTER
Body
Skin &
Body
DRG
primary
neurons
B fibers
A-β fibers
A-α
fibers
A-δ fibers
A-β fibers
C fibers
A-α fibers
interneurons
in other
segments
HTHAL
SC
MC
tertiary neurons
MDvc
VMpo VPI VPL VPM
CLVLPf
THAL tertiary neurons
CBL
BS
NRM RF
ME
Spinal Cord Map. Copyright © 2016 Arle Neurosimulation Lab, BIDMC/Harvard Medical School.. All rights reserved.

4. Spinal Cord Map. Copyright © 2016 Arle Neurosimulation Lab, BIDMC/Harvard Medical School.. All rights reserved.

5. Cervical region
Thoracic region
Lumbar region
Sacral region
Coccygeal region
Spinal Cord Map. Copyright © 2016 Arle Neurosimulation Lab, BIDMC/Harvard Medical School.. All rights reserved.

6. Odd segment
Even segment
Ventral root
Dorsal root
Mixed nerve
C1
C2
C3
C4
C5
C6
C7
C8
T1
T2
T3
T4
T5
T6
T7
T8
T9
T10
T11
T12
L1
L2
L3
L4
L5
S1
S2
S3
S4
S5
CC
Spinal Cord Map. Copyright © 2016 Arle Neurosimulation Lab, BIDMC/Harvard Medical School.. All rights reserved.

7. C1
C2
C3
C4
C5
C6
C7
C8
T1
T2
T3
T4
T5
T6
T7
T8
T9
T10
T11
T12
L1
L2
L3
L4
L5
S1
S2
S3
S4
S5
CC
DRG
Odd segment
Even segment
Ventral root
Dorsal root
Mixed nerve
Spinal Cord Map. Copyright © 2016 Arle Neurosimulation Lab, BIDMC/Harvard Medical School.. All rights reserved.

8. Spatial Relationship Between the Spinal Cord
& Spine (Vertebral Column)
The spinal cord is a single, continuous structure, but it is
considered to consist of 31 segments because of the 31
pairs of nerves associated with different regions. These
segments are grouped as follows: 8 cervical, 12
thoracic, 5 lumbar, 5 sacral, and 1 coccyceal. The
spinal cord segments are not the same as the segments
of the bone vertebral column or spine, and are displaced
such that the spinal cord starts where the spine starts but
cord ends between the spine’s L1 and L2 vertebrae (left).
(Source: Carpenter 46).
Spinal Cord Map. Copyright © 2016 Arle Neurosimulation Lab, BIDMC/Harvard Medical School.. All rights reserved.

9. Spinal Cord Measurements
Thoracic Region
Segment Transverse diameter Sagittal diameter Length Volume
T1 9.8 6.3 16.0 734.2
T2 8.9 6.2 16.5 679.9
T3 8.3 6.0 18.6 718.7
T4 8.1 6.0 19.5 755.2
T5 8.2 6.1 19.7 726.0
T6 7.7 5.7 22.3 750.0
T7 7.2 5.8 21.5 717.3
T8 7.2 6.0 18.8 647.7
T9 7.3 6.1 18.3 663.9
T10 7.6 6.3 16.2 597.1
T11 7.3 6.3 13.8 525.4
T12 7.5 6.8 12.3 516.1
Cervical Region
Segment Transverse diameter Sagittal diameter Length Volume
C1 11.3 7.7 14.3 994.3
C2 11.4 7.9 14.8 1053.8
C3 11.7 7.8 15.3 1112.7
C4 12.2 7.7 14.0 1034.2
C5 12.9 7.3 15.5 1112.1
C6 12.3 7.2 13.2 884.5
C7 11.9 6.9 12.7 789.2
C8 11.2 6.8 13.7 740.5
Spinal Cord Map. Copyright © 2016 Arle Neurosimulation Lab, BIDMC/Harvard Medical School.. All rights reserved.

10. (Sources: Ko, Gray 827-28.)TOTAL VOLUME: 18,307.7 mm3
Lumbar Region
Segment Transverse diameter Sagittal diameter Length Volume
L1 8.1 6.9 11.3 513.1
L2 8.3 7.2 10.0 483.4
L3 8.8 7.2 8.3 419.4
L4 9.2 7.1 7.3 354.0
L5 8.2 7.1 6.2 268.2
Sacral Region
Segment Transverse diameter Sagittal diameter Length Volume
S1 8.0 6.5 5.2 187.1
S2 7.0 5.7 4.7 121.8
S3 5.9 4.5 4.4 89.2
S4 5.7 4.4 4.2 71.8
S5 4.9 3.8 2.8 39.1
Coccygeal Region
Segment Transverse diameter Sagittal diameter Length Volume
CC 4.7 (top) to 2.0 (bottom) 3.6 (top) to 1.5 (bottom) 1.1 7.8
Spinal Cord Measurements
These tables show the average physical dimensions (mm) of all 31 spinal cord segments (white and gray matter
combined), organized by region. The values in red were extrapolated from available data using best fit curves. We
calculated volumes (mm3) by treating each segment as a truncated cone, where the tabulated diameters are
measured at the top.
Spinal Cord Map. Copyright © 2016 Arle Neurosimulation Lab, BIDMC/Harvard Medical School.. All rights reserved.

11. Gray Matter Measurements
Thoracic Region
Segment Segment Volume Percent Gray Matter Gray Matter Volume
T1 734.2 20 146.8
T2 679.9 17 115.6
T3 718.7 15 107.8
T4 755.2 14 105.7
T5 726.0 13 94.4
T6 750.0 13 97.5
T7 717.3 14 100.4
T8 647.7 16 103.6
T9 663.9 18 119.5
T10 597.1 21 125.4
T11 525.4 24 126.1
T12 516.1 27 139.3
Cervical Region
Segment Segment Volume Percent Gray Matter Gray Matter Volume
C1 994.3 27 268.5
C2 1053.8 31 326.7
C3 1112.7 33 367.2
C4 1034.2 33 341.3
C5 1112.1 32 355.9
C6 884.5 29 256.5
C7 789.2 26 205.2
C8 740.5 23 170.3
Spinal Cord Map. Copyright © 2016 Arle Neurosimulation Lab, BIDMC/Harvard Medical School.. All rights reserved.

12. Gray Matter Measurements
(Sources: Noback 16-22, Temple, Greenstein 5,
Gray 828, Carpenter 48, Netter 151.)
TOTAL VOLUME: 4,602.1 mm3
Lumbar Region
Segment Segment Volume Percent Gray Matter Gray Matter Volume
L1 513.1 30 153.9
L2 483.4 33 159.5
L3 419.4 35 146.8
L4 354.0 37 131.0
L5 268.2 39 104.6
Sacral Region
Segment Segment Volume Percent Gray Matter Gray Matter Volume
S1 187.1 41 76.7
S2 121.8 44 53.6
S3 89.2 47 41.9
S4 71.8 50 35.9
S5 39.1 52 20.3
Coccygeal Region
Segment Segment Volume Percent Gray Matter Gray Matter Volume
CC 7.8 52 4.1
To find the amount of gray matter in the spinal cord, we factor the calculated volume of each segment by the percent
taken up by the gray matter. This information is extracted from various pictures and diagrams available in the
literature that show cross-sections of the spinal cord at certain levels.
Spinal Cord Map. Copyright © 2016 Arle Neurosimulation Lab, BIDMC/Harvard Medical School.. All rights reserved.

13. Segment Distribution of Neurons
Cervical Region
Segment Percent Volume # Neurons
C1 5.8 5833495
C2 7.1 7098515
C3 8.0 7978838
C4 7.4 7415938
C5 7.7 7732883
C6 5.6 5573698
C7 4.5 4458698
C8 3.7 3700842
Lumbar Region
Segment Percent Volume # Neurons
L1 3.3 3344806
L2 3.5 3466317
L3 3.2 3189658
L4 2.8 2846116
L5 2.3 2272851
Sacral Region
Segment Percent Volume # Neurons
S1 1.7 1666884
S2 1.2 1164522
S3 0.9 910983
S4 0.8 780085
S5 0.4 441802
Coccygeal Region
Segment Percent Volume # Neurons
CC 0.1 88134
TOTAL # NEURONS: 100,000,000
Thoracic Region
Segment Percent Volume # Neurons
T1 3.2 3190744
T2 2.5 2511549
T3 2.3 2342537
T4 2.3 2297405
T5 2.1 2050820
T6 2.1 2118616
T7 2.2 2182109
T8 2.3 2251861
T9 2.6 2596706
T10 2.7 2724671
T11 2.7 2739990
T12 3.0 3027926
These tables show our lab’s neuron count for all 31 spinal
cord segments.
(Source: Longstaff 15-16 .)
Spinal Cord Map. Copyright © 2016 Arle Neurosimulation Lab, BIDMC/Harvard Medical School.. All rights reserved.

14. Distribution of Neurons in Rexed laminae
Based on the segment distribution and published data such as size of neurons of different types known to predominate in each
lamina (Noback 16-22, Temple, Greenstein 5), we calculated the number of neurons in each Rexed lamina of each segment of
the spinal cord. A sample is shown on the next slide.
A paper containing the methodology of the work in these slides and full data set in a supplement is being prepared for
publication (June 2016).
Cervical
Thoracic
Lumbar
Sacral Coccygeal
Spinal Cord Map. Copyright © 2016 Arle Neurosimulation Lab, BIDMC/Harvard Medical School.. All rights reserved.

15. 0
5
10
15
20
25
30
35
40
1 2 3 4 5 6 7 8 9 10
PercentVolume(%)
Lamina Number
Segment T9
Lamina % Volume # Neurons Weighted Scaled 1:20
I 3 77901 1167 23
II 10 259671 1556545 31131
III 9 233704 105067 2101
IV 10 259671 25942 519
V 4 103868 31131 623
VI 0 0 0 0
VII 34 882880 264613 5292
VIII 13 337572 303526 6071
IX 11 285638 28537 571
X 6 155802 280178 5604
TOTAL 100 2596706 2596706 51934
0.020
0
200000
400000
600000
800000
1000000
1200000
1400000
1600000
1800000
0 1 2 3 4 5 6 7 8 9 10 11
NumberofNeurons
Lamina Number
0
5000
10000
15000
20000
25000
30000
35000
0 1 2 3 4 5 6 7 8 9 10 11
NumberofNeurons
Lamina Number
Spinal Cord Map. Copyright © 2016 Arle Neurosimulation Lab, BIDMC/Harvard Medical School.. All rights reserved.