By DR. W.N. DUDLEY, D.A.B.C.T. and Richard W. Merritt, D.C.. D.A.B.C.T.
W.N. Dudley, D.C., is a postgraduate lecturer at Palmer and Texas Chiropractic colleges. He has been using thermography since 1970. He is a past president of the International Thermographic Society and is also a diplomate of the American Board of Clinical Thermology and a member of the board. Dr. Dudley is board certified in thermography by the ACA. 'He has authored numerous articles on thermography and related subjects. On September 25, 1990, Dr. Dudley attended the Fifth European Congress of Thermology in Cesena, Italy. Currently, Dr. Dudley practices in Howell, Mich.
Richard W. Merrilt, D.C., is a 1973 graduate of Iowa State University and a 1976 graduate of Palmer College of Chiropractic. Dr. Merritt is a board qualified clinical thermographer and a diplomate in the American Board of Clinical Thermology. He is a member of a number of chiropractic organizations including the American Chiropractic Thermographic satiety, Christian Chiropractic Association, Florida Chiropractic Society, In~ernafionnl Academy of Clinical Thermology, International Chiropractic Association, International Thermographic Society, National Academy of Thermology, Pi Tau Delta, International Chiropractic Honor Society, and the Texas Chiropractic Association.
Meralgia paresthetica has been described as an occurring neuropathy having varied thermal display when measured by thermography.1 Ecker, using liquid crystal thermography, found a thermal response of isothermic, hyperthermic, and hypothermic display in a study of 14 cases. Gateless, using liquid crystal thermography, found similar results in her study of 11 cases.2 In this study we also found the thermal measurement to be somewhat inconsistent using electronic means but an additional thermal variable has been noted.
Anatomy
The lateral femoral cutaneous nerve (LFCN) is entirely sensory, it is derived from the posterior roots of the second and third lumbar nerves. After emerging from the lateral aspect of the psoas major muscle, the nerve crosses the iliacus muscle and continues toward the anterior superior spine of the ilium by turning upward sharply from the deep circumflex iliac vessels and passes beneath the fibrous attachment of the internal oblique muscle of the abdomen. It usually continues medial to the anterior superior spine of the ilium and under the inferior portion of the inguinal ligament but may pass under or even lateral to the origin of the sartorius muscle. The nerve passes inferiorly, about 4 cm. below the inguinal ligament, and pierces the fascia Iata. The main or anterior branch remains beneath the fascia of the thigh; becomes superficial about 9 cm. below the inguinal ligament, and supplies the skin of the thigh down to the knee. The small posterior branch soon becomes superficial and supplies the skin from the greater trochanter down to the area supplied by branches from the anterior division. The arcuate fibers of the fascia lata tend to protect the nerve from compression.
Method
Patients examined in this present study were equilibrated and a lower scan was done. It was the bilateral gateleg as well as anterior and posterior thigh views that were of interest. An Inframetrics 520 with computer and software was used. The software allows for isothermic presentation to compare and quantify with fractional degrees at an accuracy of .010C. in the black and white mode. A 10 color presentation can also be displayed. Four images can be displayed at one time in black and white and isotherms continues medial to the anterior I can be used which allows for the measurement to .010C. accurately on all views simultaneously. Color thermograms due to their inherent error may lead to undiagnosed neuropathies in cases where the thermal gradient is relatively small.
The quantification has several benefits. First, the neuropathy can be located and qualified as existent. Second, if the patient is acute, rapid quantification on succeeding days allows for the conclusion that recovery is being achieved by the applied therapy if thermal measurements move toward symmetry. Third, the patient may be mobile and asymptomatic after treatment but the thermal emission has not equalized, which would necessitate further care. Fourth, the same quantification may delineate that the recovery of the LFCN cannot be done, either the patient has a permanent deficit and will not recover or the adjustment will only minimize the complications of the loss or there is an underlying process that affected the LFCN that does not respond to spinal manipulation.
Etiology
There are several theories proposing the origin of MP and they ran be divided into either infectious processes or one of local pressures.4 Obesity is given as a causative.5 In this study the weights varied from 110 pounds to 216 pounds with the average being 148 pounds. The existence of subluxation at the second lumbar 6 would seem to be of great importance although neuritis, flat feet and tight clothing has also been mentioned.7
In 1925 Rosenheks8 stated that MP was a secondary expression of osteoarthritis of the spine but little has been noted since that view was expressed. In this study, only two cases had spinal changes consistent with slight osteoarthritis. The changes were not focal to the upper lumbar area. And both cases had discogenic changes at L5-S1.
Posture has also been associated as a causal factor of MP 9,10 and four of these cases were severely antalgic, were able to stand only briefly, but none of the four described any numbness or pain in the lateral thigh or knee. They could not describe subjective anesthesia at the lateral thigh upon examination, Six cases did describe knee pain but it was a minor complaint. Cases 2, 9 and 10 were able to describe numbness to touch without examination prior to entry (see Table 1).
| Table 1 | Age | LFCN | SMPS | |
| 1. | JWP | 39 | 0.50 | 0.90 |
| 2. | DJT | 48 | 0.75 | 0.55 |
| 3. | DRB | 31 | 1.00 | 0.70 |
| 4. | DBH | 44 | 0.45 | 0.45 |
| 5. | DLG | 25 | O.a5 | 0.45 |
| 6. | MEF | 64 | 0.80 | 1.30 |
| 7. | PCA | 50 | 0.45 | 0.30 |
| 8. | PGP | 43 | 2.00 | 0.00 |
| 9. | RRP | 43 | 0.50 | 0.60 |
| 10. | STS | 32 | 0.00 | 0.65 |
| 11. | KNO | 17 | 1.70 | 1.75 |
| 12. | RNB | 24 | 0.40 | 0.45 |
| 13. | AAK | 17 | 0.65 | 0.65 |
| 14. | TLR | 30 | 1.30 | 0.20 |
Cases 6 and 7 had attendant vascular disease which complicated the evaluation of the scan and made the diagnosis of MP more difficult. But, allowing for increased thermal emission from the vein, the loss in the distribution of the LFCN was not difficult to ascertain.
FIGURE 1.
Case 11 described trauma, but was not antalgic, had no knee pain and described the trauma as a pain upon lifting a rather light object that was lifted often and the thermal measurements were nearly equal at the lateral thigh and posterior knee. None of these cases had surgeries or fractures.
In this study,14 cases were examined not only in the LFCN area but also at the superior medial popliteal space (SMPS). In all cases except one, the SMPS displayed an increase in thermal emission which appeared as a vertical stripe following the lower portion of the semimembranosis muscle and its insertion into the medial condyle of the tibia (Figures1,2, 3).
FIGURE 2.
FIGURE 3.
Ecker suggested that MP started in middle age, in this study the average age was 36. In many cases the disorder is found by thermography and not suspected. In the case that presents as acutely antalgic with back pain, MP could easily be missed. The thermographic examination could be thought to be compromised since the patient has not done prior preparation, but that doesn't apparently compromise the thermal findings to establish MP. In four cases that were severely acute, a thermographic scan was done, the LFCN and SMPS could be seen to be displaying unevenly and initial treatment could be given. As the case reenters, succeeding scans could be done and the later scan may give a clearer thermal evaluation to delineate the problem.
Following Ecker's comment that a small elliptical area at the anterio lateral region was sensitive to diminished sensation of pinprick,11 this was the area quantified by the isotherm and utilized for thermal measurements in these cases as seen in Table1. The LFCN thermal variant display often showed very large when under examination in the electronic format. However, we isolated the display to this small area. No significance was given for the length of duration of the disability to see if duration caused an effect on isothermia, hypothermia, or hyperthermia. Unfortunately this study does not add new information to that question. The measurement was done and the elliptical area showed the smallest and most critically measurable display as compared to the opposite side. The thermal display varied from zero to 2.O0C. with an average of .780C. at the LFCN. The SMPS varied from zero to 1.750C. with the average being .640C.
Four hundred scans were reviewed utilizing electronic infrared. On this equipment 16 colors were displayed using an 8 degree range. These 400 cases were mostly automotive whiplash trauma cases and had low incidence for back or leg pain. These cases consisted of 245 women (or 62%) and 155 men (or 38%). The total number of MP diagnosed by thermography was 120 cases; with 69 women (or 58%) and 51 men (or 42%) with the occurrence being 30 percent. There were 9 cases (or 2%) not displaying a heated area at the SMlPS. The stripe was at varying display with some cases showing a long heated stripe while others had only a mild thermal increase. No delta T's were attempted due to the use of color thermography and the inherent error. The information gained would seem to confirm that antalgia and spasm is not an uncommon finding in MP. But there is little to verify that knee pain is a symptom heralding the problem even though there is distinct thermal emission at the SMIPS.
In some cases there was not a rapid recovery. Often the asymmetric residual at the LFCN forces the conclusion that the loss will recur or the adjustment lacks some capacity to cause complete response or there is an underlying complication that is not obvious. It has been noted before that once a neurologic deficit occurs complete recovery is not always the case. It has been noted that the chiropractic adjustment does cause correction to this neuropathy but there may be a residual that does not respond.12,13 This study would confirm that opinion. The patient continues to evidence the thermal variance which may be seen thermographically even though they are asymptomatic.
The thermal variant is often small at both the LFCN distribution and at the SMPS area and can be easily overlooked unless great care is exercised evaluating thermograms.
References
1. Dudley, W.N. Peripheral nerve loss seen by thermography, ACA Journal of Chiropractic, Vol. 18-11-63, Nov 1984.
2. Ecker, A.D., Woltnan, H.W. Meralgia paresthetica: A report of 150 cases, JAMA, 1938; 110:1650-1652.
3. Gateless, D., Di Gullis, P., Ingall, F.R.F., Mahmud. M.Z.. Gilmy. G. Thermography in meralgia paresthetica, Neu rology 33:5, r983.
4. Gateless, D., Gilroy, I. Tight jeans meraIiga: Hot or cold. JAMA 1984; 252:42-43.
5. Kelly, J.J. Jr., Focal neuropathies of the leg, Spine: Vol. 2, No. 4, Sept 1988, 699- 712.
6. Dudley, W.N. Thermography, Christianson, J.; Gerow, G.; Ed. Williams and Wilkins, 1990.
7. Chusid, J.C;. Correlative Neuroanatomy and Functional Neurology, E. Norwalk, CT, Lange Medical Publications,1985.
8. Rosenheck, C. Meraliga paresthetica: its relation to osteoarthritis of the spinal vertebrae, JAMA 85:416-417, Aug 1925.
9. Boyce, J.R. Meralgia paresthetica and tight jeans, JAMA, 1984, 251, 1553.
10. Kadel, R.E., Godbey, W. D. Meralgia paresthetica; a study of incidence, Journal Manipulative and Physiologic Therapeutics, 6, 2, 1~83.
11. Ecker, A.D. Diagnosis or meralgia palresthetica, JAMA, Feb 15, 1985, Vol. 253, No. 7.
12. Dudley, W.N. Distal thermographic residuals: double lesion neuropthy, ACA Journal of Chiro, Vol. 25-5-32, May 1989, 67-69.
13. Dudley, W.N. Thermography: tracking nerve traps, ACA Journal of Chiro, March 1987, Vol. 21-3-63.1
ACA Journal of Chiropradic December 1990