Ruben Pochaczevsky 1

Frieda Feldman 2

Received June 18, 1981; accepted after revi­sion December 18, 1981.

I Department of Radio logy, Long Island Jewish­Hillside Medical Center, New Hyde Park, NY 11042. Address reprint req uests to R. Pochaczev­sky.

' Department of Radio logy, Columbia-Presby­terian Medical Center, New York, NY 10032.

AJNR 3:243-250, May/ June 1982 0195-6108/ 82 / 0303-0243 $00.00 © Ameri can Roentgen Ray Society

Contact Thermography of Spinal Root Compression Syndromes

243

A thermographic technique is described that uses cholesteric liquid crystals that change color in response to variations in surface temperature. The crystals are em­bedded in elastic flexible sheets that conform to the contours of the torso and extremities. The technique is well suited to temperature measurement of individual skin dermatomes and myotomes. Typical heat patterns emanating from the torso and extremities have been observed and correlated with root compression syndromes at low cervical and low lumbosacral levels. The imaging results correlate well with clinical and surgical findings, particularly when the extremity dermatomes are included. The technique objectively documents the subjective complaint of pain and approaches myelography in accuracy. It was in agreement with myelography in 86% of cases and with surgery in 95% of cases. Liquid crystal thermography may, therefore , effectively screen patients for myelography and can complement it in identifying clinically signifi­cant abnormalities.

A noninterventional method , contact thermography , is described that uses cholesteric liquid crystals that undergo spec ific co lor changes in response to temperature changes. These properties have been used previously for contact color thermography [1 -3]; we successfully used them in the detecti on of breast cancer [4 ,5]. Elasti c " Flex i-Therm " sheets (Flex i-Therm , Inc., Westbu ry, N.Y.) containing the thermally sensitive liquid crystals can be contoured to the extrem­ities and torso by using a new device, an " air pillow" box (Flex i-Therm). Uniform skin contact with resultant consistently reliable thermograms have thereby been achieved. To date , spinaLroot compression syndromes have been conventionall y diagnosed only by c linical means, electromyography , mye log raphy , and , most recently, by computed tomography (CT). We found contact thermography valu­able for screening and for identifying spinal nerve root compression.

Materials and Methods

Our material consists of 88 patients with c lini ca l diagnosis of spinal root compression syndromes; 57 had myelograms and 37 were treated surg ica lly. The apparatus (fig . 1 A) consists of an hermetica lly sealed box , 37 x 38 x 3.5 cm, one side of which has a transparent plastic wa ll , while the oth er is composed of liquid crysta ls embedded in an elastom eric sheet. Air pumped into th e box by a foot pump di stends the sheet in to a compliant convex surface (fig. 1 B) sui table for contact th ermography (fig . 1 C).

Cholesteric liquid c rystals have accurate and reliable color responses to spec ific tem­perature changes (table 1). The lowest temperature is d isplayed as a dark brown color and c hanges with progressive temperature elevation to tan , redd ish brown, blue, and dark blue. Six or more air pillow boxes are available; they are numbered 26- 35, correspond ing to the med ian Celsius temperature ranges of their incorporated liquid c rystal Fl ex i-Therm sheets . An instant camera with an electron ic fl ash system and cross-po larized filter records color thermograms. A fi xed-d istance frame attached to the camera provides support for the air pillow and facilitates photography (fig . 10).

244 POCHACZEVSKY AND FELDMAN AJNR :3 , May / June 1982

A 8

TABLE 1: Typical Liquid Crystal Elastomeric Sheet Temperature Calibrations

Sheath ( Oc)

Color 32 33

Dark brown ........ 31 .2 32.0 Tan 3 1.6 32 .3 Reddish brown ....... . . 3 1.9 3 2.7 Yellow 3 2.2 33.6 Green . . . . . . . . . . 32 .4 33.7 Light blue 33.2 34 .6 Dark blue 35 .0 36 .0

34

32 .9 33 .2 33 .4 3 4 .0 34 .2 35 .3 3 6.4

Note.- These calibrations permit determinations of temperature differentials (.aT O) in comparable regions p f the spine and ex tremi ties.

Technique

The examination is performed in a draft-free air condi­tioned room with an approximate temperature of 20°C. The skin temperature of the back is stabilized by sponging with water and cooling for 10-15 min. A hair drier set on "cool " can further expedite skin drying and cooling. Sponging of the extremities is unnecessary. Patients should not smoke on the day of the examination since smoking may affect skin temperature [7].

The air pillow with the widest display for the patient' s skin

INflATED CRYSTAL MATERIAL 7

c

Fig . 1.-A, Liquid crystals in elastomeric sheet (a) mounted in air pillow (b) inflated by small pump (c ). B, Inflated air pillow. C, Contact thermogram, posterior thighs. D, Recording system . (Reprinted from [6].)

Fig . 2.-Body derm atomes. (Modified from [8].)

temperature is selected . A 30°C box is used initially. If brown colors seem to predominate, the skin temperature is too cold for that particular box since brown represents the lowest temperature on the liquid crystal color scale (table

AJNR:3, May / June 1982 CONTACT THERMOGRAPHY OF SPINAL ROOT COMPRESSION 245

LOW ER CERVICAL

5TH CERV I C AL 6 TH CERV I CAL

7 TH CERV I C AL 8T H CERVICAL

LU,\1B OSACRAL

4TH LUMBAR 5T H LC)-l BAR 1ST SACRAL

( \ I \

\ ) ~ Fig. 3. -Dermatome chart. Common single nerve root syndromes. (Mod­

ified from [8].)

Fig. 4 .-Normallumbosacral contact thermography. A , Lower back view.·Cen­tral zone of decreased heat emanation in region of spinous processes (white arrow) and intergluteal fo ld (black ar­row). Normal symmetric heat patterns in posterior gluteal reg ions (B) and thighs (C); oblique right (0) and left (E) gluteal; anteri or thighs (F); lateral right (G) and left (H) thighs; and dorsum of feet (I).

A

o

G

1). A 28 °C box is then substituted. If blue colors predomi­nate with the 30°C box , the skin temperature is too warm since blue represents the highest temperature on the liquid crystal co lor scale. If this happens, a 32 °C box is used. The appropriate box is then firmly pressed against the patient's extremities. A colored image promptly appears on the liquid crystal sheet. The box is then slightly lifted from the sk in surface to eliminate distortion and glare and the image is immediately photographed .

Routine views of the lumbosacral region and lower ex­tremities consist of separate images of the lumbar reg ion ; buttocks; anterior, lateral, and posterior aspects of both thighs; anterior, lateral, and posterior aspects of both lower legs including the ank les; and the dorsal aspect of the feet , including the toes.

Routine images of the cervical spine and upper extremi­ties include views of the posterior neck; both posterior shoulders; posterior, anterior, ulnar, and radial aspects of the forearms ; and the dorsal and palmar aspects of the hands and fingers . Abnormal thermographic images should be repeated at least three times in succession to confirm their orientation to spec ific dermatomes and myotomes (figs. 2 and 3) [8].

A normal thermogram of the spine and extremities shows symmetrical heat emission, while root lesions have been

B

E F

H

246 POCHACZEVSKY AND FELDMAN AJNR:3. May / June 1982

associated with temperature changes in the corresponding derm atomes and myotomes [6 , 9-14). The temperature changes may be related to reflex sympatheti c vasoconstri c­ti on within affected extremity dermatomes and metabolic changes or muscular spasm in corresponding paraspinal myotomes. As a rul e, temperature changes appear as zones of hypothermi a in the affec ted extremity derm atomes [6 , 9-14). However, we found that hyperthermi a occurs , parti cu­larl y in the hands and feet. Both hypothermic and hyper­thermi c reac ti ons are abnorm al, since there shou ld be no significant temperature difference between either side of the sp ine or between the ex tremities in norm al individuals [1 5-20). Thi s was confirmed in our c linical experi ence, the exception being the occasional inc rease in temperature of the dominant arm and posteri or forearm in ve ry muscular males .

A norm al thermogram of the spine (fi g. 4) is characterized by a central zone of decreased heat emanation in the region of the spi nal processes from the cervi ca l spine down to the lower lumbosacral spine. The intergluteal fold is also re­corded as hypothermic since it is not in contact with the liquid crystal sheets. The sacroiliac joints may show sym­metrica l loca lized inc reased heat emission [1 9, 20). A pos­iti ve or abnorm al therm og ram will show evidence of asym­metri c inc reased heat production at myotomes in the lower lumbosacral reg ion and asymmetri c dec reased heat produc­tion lateral to the mid line along the cervica l thoracic and upper lumbar spine.

Results

The find ings in the 37 surgica l cases are detailed in table 2. Contact thermography showed no false-negatives whi le mye log raphy was equivocal or falsely negative in six pa­ti ents, all of whom had surgica l evidence of root compres­sion. Three of these six had superior facet hypertrophy or lateral recess stenosis and three had hypertrophic spurs and / or herni ated di sks. There vve re two false-pos itives by contact thermography and no false-positives by mye logra­phy (table 3).

In eight operated cases in whi ch contact therm ography and myelography disag reed, thermog raphy was fu ll y correct

TAB LE 2: Root Compression Syndromes: Surgical Findings

Causes. Locations of Root Compression

Hern iated d isks, face t entrapmen t. osteophyte impingement, and / or spinal stenosis:

L5 S1

Spinal stenosis and facet en trapment , L4 Ex trad ura l metastasis, S1 Neurofibroma:

S1 C6-T3

Ependymoma, L3 Syringomyelia, C3-C7

Note.-Sorne findings were at two or more levels.

No . Pat ients ( 11 = 37)

25 11

3 2

TABLE 3: Comparison of Contact Thermography and Myelography: Operated Patients

No. Operated Pal lents

Thermography M yelograpt,y

Tru e-Posit ive 34 30 True-Negati ve 1 1

False-Positive 2 0 Fa lse-Negati ve 0 6

Total 37 37

Accuracy (% ) 95 84

TABLE 4 : Comparison of Contact Thermography and Myelography

Myelograpll Y Contact Thermography

Positive Negative Totals

Positive 37 8 45 Negati ve 0 12 12

Totals 37 20 57

in six cases and partl y correct in one case. If only completely correct results were compared with surgical finding s, the overall accuracy of contac t thermography was 95% and that of myelography 84% (table 3).

Surgery was performed on on ly one of 1 2 pati ents with both a normal thermogram and mye logram. Although lateral spinal recess stenosis was found at the fifth lumbar level, there was no evidence of root compression at surgery . This case is considered a true-negati ve, although it may have conceivably caused intermittent root compression. Ther­mography was in agreement with myelography in 8 6% of 57 pati ents. Other correlations with mye lography are shown in tables 3 and 4 .

Discussion

Contact thermography appears to be particularly well suited for the di agnosi s of root compression syndromes [6, 9). Typical heat pattern s have been observed in thi s study. S1 root involvement is assoc iated with loca lized increased heat emi ssion from the affected side of the lum­bocacral reg ion . The ipsilateral posterior thighs, and , in most cases, posteri or and lateral aspects of the leg show hypothermia whil e concomitant hyperthermi a or hypother­mia is seen along the lateral aspects of the foot and fifth toe. The inferomedial ipsilateral buttock may also show hypothermia (fi g . 5) .

L5 root involvement is usuall y characterized by hyper­thermia in the corresponding side of the lumbar spine, usuall y radiating laterally; hypothermi a of the ipsilateral midgluteal reg ion, outer aspects of the thigh , and anteri or leg; and hyperthermia or hypothermi a of the dorsum of the foot and f irst through fourth toes (fi gs. 6 and 7) .

C6 root compress ion syndromes are usuall y assoc iated with hypothermi a of the ipsilateral posteri or cervical mus-

AJNR:3 , May / June 1982 CONTACT THERMOGRAPHY OF SPINAL ROOT COMPRESSION 247

A

c

B

o Fig . 5. -Right S1 syndrome, 48-

year-old woman with right leg pain due to surgically proven herniated L5-S1 disk . A, Gluteal reg ions. De­creased heat emission (darker brown) from right buttock and right inferomedial gluteal region ( arrow) compared with left . B , Posterior thighs. Decreased heat emission (less green) from right thigh (a rrow ) compared with left . C and 0 , Lower legs, lateral views. Posterolateral as­pect of right leg (C) is cooler (brown, arrow) than same region in left leg (D) (arrow). E, Myelogram. Hight L5- S1 interspace defect (arrow) with amputation of S1 nerve root.

cles, posterior shoulder, radial side of the forearm, and a hot or cold thumb (fig. 8). C7 root involvement is associated wi th hypothermia of the ipsilateral posterior cervical spine muscles, posterior shoulder, and dorsal aspect of the fore­arm. Hyperthermia or hypothermia of the ipsilateral second and third fingers is also seen in most cases. C8 root involve­ment is associated with hypothermia of the ipsilateral pos-

Fig . 6.-Right L5 root compression syndrome, 64-year-old woman with backache and pain in both lower extremities due to osteophytes and spinal stenosis (surgery) . A and B, Lateral views of thighs. Decreased heat emission in righ t thigh (A) (reddish brown , arrow ) compared with left (B) , which shows increased heat emission (green, arrow ). C and 0 , Anteromedial aspects of

A B

c o

E F

legs. Right leg (C) shows decreased heat emission (brown, arrow) compared with left leg (D), which shows increased temperature (green and blue, arrow) . E, Dorsum of feet. Dorsum of right foot shows increased heat emission (blue and green, arrow) compared with left . F, Myelogram . Partial block at L4-L5 interspace (arrow ).

248 POCHACZEVSKY AND FELDMAN AJNR:3, May / June 1982

B c

D

Fig . 7.-Lelt L5 root syndrome, 49-year-old man with back pain rad iating to lelt leg. A, Lumbar area. Hot zone (green, upper arrow) and cold zone (brown , lower arrow) in lelt buttock . B and C, Lateral thighs. Lelt thigh (B)

A

c

D

Fig . 8. -Right C6 root compres­sion syndrome, 64-year-old woman with burning sensation in both hands, espec ially right. A and B, Posterior shoulders. Right shoulder (A) is co lder (brown, arrow ) than left (B), which is warmer (green, arrow) . C, Radial aspects 01 lorearm s. Right

. lorearm (straight arrow) and thumb ( curved arrow ) are colder (less green) than left . D, Myelog ram. Par­tial block at C5-C6level due to larg e localized osteophytes.

terior cervical spine muscles, posterior shoulder, and ulnar aspects of the forearms. Hyperthermia or hypothermia of the ipsilateral fourth and fifth fingers is frequently noted .

We believe that thermographic accuracy in diagnosing spinal root compress ion syndromes is greatly improved when a simultaneous study of extremity dermatomes is

cooler (less blue) than lateral right (C). D, Dorsum, lirst, second , and third toes (arrow) of lelt loot are warmer (blue) than right. (A and D reprinted from [6]'

AJNR:3, May/June 1982 CONTACT THERMOGRAPHY OF SPINAL ROOT COMPRESSION 249

included [6, 9-14]. This was documented in over one-third of our surgically proven positive cases where thermographic patterns in the lumbosacral region were either normal or inconclusive, A correct diagnosis was made, however, with definitely abnormal thermographic patterns in the extremi­ties that adhered to known anatomic dermatome distribu­tions (figs. 5 and 6).

The differential diagnosis of spinal root compression syn­dromes includes deep venous thrombosis [21], ischemic arterial disease [22], local trauma, and arthropathies of extremity joints [23]. These can be distinguished from spinal root compression syndromes in most cases by their distinct clinical pictures and by the failure of thermographic findings to be confined to a definite skin dermatome distribution . Varicose veins can be distinguished by their serpiginous course on the thermograms [21].

In the upper extremities, the differential diagnosis includes carpal tunnel syndrome with median nerve irritation and the ulnar nerve entrapment syndrome [24]. In med ian nerve involvement, there may be temperature changes in the thumb, second and third fingers , and radial side of the fourth finger. The ulnar nerve entrapment syndrome is usually associated with a cold dorsal forearm and temperature changes in the fourth and fifth fingers (Pochaczevsky R, unpublished data). In leprosy, hypothermic areas, as noted on thermography, are the sites of most marked sensory loss [25].

Root compression syndromes usually show hyperthermia in the lumbosacral and hypothermia in the cervicothoracic regions of the ipsilateral adjacent paraspinal myotomes. Musculoligamentous injuries of the spine and or osseous lesions without root compression appear to have thermo­graphic changes localized to the spine [18]. They are not usually associated with thermographic changes in the ex­tremities. Peripheral nerve trunk compression syndromes may cause hypothermia in their territorial distribution (fig. 9) .

Simultaneous contact thermography and conventional in­frared telethermography were performed on over 50 pa­tients in a private practice setting . We could not include these patients here because our research was restricted to hospital patients. However, preliminary results indicate good correlation between these two thermographic techniques . Advantages of contact thermography over electronic in­frared telethermography are low price , simplicity of appa­ratus, and high color contrast. The chief advantages of telethermography are that contact with the patient's skin is not req uired and larger body areas can be encompassed on each view.

Our preliminary results indicate that diagnostic accuracy of nerve root compression comparable to or better than by myelography (tables 2-4) may be achieved with contact thermography . This is true with the proviso that extremity dermatomes are included as part of the basic thermographic examination . Contact thermography is a noninvasive tech­nique that appears to have high sensitivity and correlates well with clinical and surgical findings. In our c linical expe­rience, negative thermograms were always associated with negative myelograms and a benign clinical course (table 4). There were no false-negative thermograms in the surgically

c o Fig . 9.-Right peroneal nerve syndrome due to cystic fibroma (surgery) .

Right ankle and lower leg (A) show decreased heat emission (light brown) along anterolateral aspect compared with corresponding reg ion of left lateral lower leg and ankle (B), wh ich shows appreciable heat emission (g reen). e, eT of legs at neck of fibulas. Well ci rcumscri bed, relatively radiolucent lesion (arrow) in peroneal nerve.

treated cases (table 3). Thermography may, therefore, ef­fectively serve to screen patients for myelography and can complement myelography in identifying c linically significant abnormalities. In another reported seri es of 130 patients, thermography of the spine and extremities was 93% accu­rate as compared with physical findings, while electromyog­raphy was only 82% accurate [14].

Our c linical experi ence shows that contact thermography can objectively document the subjective complaint of pain. Demonstrable alterations in surface temperature corre­sponding to the distribution of pain or spec ific root derma­tomes strongly suggest that a somatic abnormality exists despite other normal examinations inc luding myelography.

ACKNOWLEDGMENT

We thank Seymour Katz fo r technical assistance.

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