SENSIBILITY TESTING AFTER NERVE GRAFTING

R. W.M. Keunen* and A.C.J. Sloofj*

SUMMARY

This study attempts to establish which sensitivity test is to be preferred for final assessment of recovery of

sensibility after nerve grafting. For this purpose seven sensibility tests were performed on patients who had been treated by median

nerve transplantation. The findings revealed that the stereognosis test is of greater value for a final evaluation than the two-point discrimination test. This paper discusses several aspects of sensibility tests.

e.g. the range of variation of the results and the degree of objectivity.

INTRODUCTION

This study attempts to establish which clinical sensibility test is to be preferred in

demonstrating recovery of sensibility in patients with a free autograft of the median

nerve.

Peripheral nerve lesions are quite common, and the chance of recovery from these

lesions has greatly improved in the past twenty years. The use of the operating

microscope (SMITH 1964) and interfascicular grafting (MILLESI 1972) have consider-

ably contributed to this. The literature shows no agreement on the sensibility test of

choice to demonstrate this recovery. Most authors apply the criteria for sensory

recovery recommended by the British Medical Council (SEDDON 1954) see Table 1).

In this classification the two-point discrimination test (2PD test) occupies a

prominent position.

IABLt 1.

so = Absence of sensibility. SI = Deep cutaneous sensation in the autonomous zone. s2 = Some degree of superficial pain sensation and tactile sensibility. s2+ = Tactile and pain sensation throughout the autonomous zone with persistent over-

reaction. s3 = Same as S 2 +, without overreaction. s3 + = Good localization of stimuli and some return of two-point discrimination. S4 = Complete recovery.

* Department of Surgety, St. Elisaberh Hospital, Tilburg, The Netherlands.

** Department of Neurosurgery. De Wever Hospital, Hearlen, The Netherlands.

Clin. Neurol. Neurosurg. 1983. Vol. 85-2 (Accepted 93.83)

ISSN 0303-8467

94

Assessment of sensory recovery after nerve grafting is important for several reasons. A reliable sensibility test makes it possible to compare operative results and different operative techniques. It is also important to obtain reliable data on the degree of invalidity of patients treated by nerve grafting.

Assessment of sensibility is a subjective activity. It is subjective in that the patient has his specific background, intelligence and ability to cope with the lesion and the operation; it is subjective also because the physician has to evaluate the results of operations which he himself has performed. These factors determine differences in the results of sensibility testing.

This study was designed as an attempt to assess the importance of these dif- ferences. The testing was done by one physician who had not performed the operations and did not know the patients. Using several testing techniques, six patients were examined repeatedly and very carefully. Although the different test- ing techniques were not always sufficiently quantifiable for exact comparison. the entire battery of tests provided sufficient data for proper evaluation of sensory recovery after nerve grafting. This procedure prompted this publication.

In order to establish which sensibility test is to be preferred for evaluation of sensory recovery after nerve grafting, seven different sensibility tests were applied. They were performed repeatedly and very carefully on both hands of patients treated by medial nerve grafting after total severance of this nerve. The results of the various sensibility tests were subsequently compared.

METHODS AND PATIENTS

1. Thepin test

The area innervated by the transplanted median nerve is demarcated with the aid of a pin-point. The size of this area is indicated on a localisation chart of the hand.

2. The brush test

The patient is asked whether he perceives the touch of a thin nylon brush in the area identified with the aid of the pin test.

3. The head/point discrimination test (HP test) The patient is asked whether he can discriminate between pin-head and pin- point in the area identified with the aid of the pin test.

4. The temperature sense test

The patient is asked whether he perceives a difference between a test tube tilled with cold water (0°C) and one filled with warm water (30°C) in the area iden- tified with the aid of the pin test.

5. The two-point discrimination test (2PD test) Two-point discrimination is determined with the aid of calipers weighing 35 g, applied transversely to the corresponding fingers on the untreated and the treated side. Since in this group of patients the test results for the second fingers proved to be representative of the difference between the untreated and the treated side, these results were listed in Table 2.

95

The Locagnosis test i~~~~lizut~~n of rnctiie ~t~~~~i~ ~~AM~UR~ER 1980) The patient puts on spectacles with deep-red glasses which can be blinded via a cable operated by the investigator. The investigator lowers the blind and, using a red pencil, marks dots at pre-set sites on the volar aspect of the hand. When the blind is lifted, the patient is unable to see these dots. The blind is lowered again and a Von Frey test hair with a continuous pressure of 49 mN is used to touch a random dot. Immediateiy after this the blind is lifted and the patient is given a black pencil with which he is asked to mark the site at which he has perceived the touch of the test hair. The distance between the red dot and the black dot indicates the patient’s ‘locognostic’ ability. The deviations found are ~raphica~Iy represented in Table 3. The s~~~e~g~~~~s test

Several materials and objects of varying size, shape and substance are used in this test. The first three fingers are used to touch the objects, and the time required to identify them is recorded. If this time exceeds 20 seconds, then the object is regarded as not identified. If the patient fails to identify the object with the unaffected hand as well, then this object is not counted in the final assessment. This final assessment is expressed in percentage which depends on the ratio between objects identified and not identified {see Table 4).

TABLE 2. Two-point discrimination test

L

.~ Test 1 2 3 4 5

A 3014 9f4 8/S 12/4 12iJ B 9/4 s/3 5/3 l/4 S/3 C 5/4 5/4 5/3 5/3 5/4 D to/3 IO/3 II/4 II/4 913 E 415 315 7/5 unreliable F 9/5 iI/5 Iii5 1013 IIf5

Two-point d~scr~m~~at~on treated hand~u~trea&ed hand. in mm.

The group of patients studied comprised five males and one female. None had any affection other than the traumatic lesion of the median nerve. This lesion was unilateral and total, leaving the ulnar and the radial nerve intact. The operations were performed 2-18 months after the accident. The operations consisted of nerve autografting performed secondarily by means of micro-techniques, making use of four or five fasciculae of the lateral cutaneous sural nerve. Wound healing was undisturbed. A postoperative EMG was recorded in all cases. A survey of the patients and of the postoperative EMG findings is given in Table 5 and Table 5, respectively.

During sensibility testing a screen was used to prevent the patient from seeing what was happening to his hands.

96

.a

.Ln

.-A-

m

.N

0 Ln

L

0 !Jl

97

IABl.lz 4. __-.-.-. -.-

Test 1 2 3 4 5

A 90% 90% 80% 801 60%

B 40% 30% 60% 40% 30%

c 20% 30% 30% 20% 20%

D 808 60% 80% 804 80%

E 20% 10% 20% 30% 40%

F 10% lo?, 2w 20% 30%

Stereognosis test

RESUL.TS

Anamnestic data showed that four of the six patients had been quite satisfied with the function of the hand after nerve grafting. The remaining two patients (E and F) had not been satisfied.

The temperature sense, brush and HP tests revealed no abnormalities. The 2PD test on the untreated side averaged 4 mm in all cases; on the treated side it ranged from 5 mm to 14 mm (Table 2). The locognosis test was performed once on patients B, D and F and revealed no abnormalities (Table 3). The scores of the stereognosis test ranged between 10% and 90% and showed some slight intraindividual variations (Table 4).

DISCUSSION

This study was made at least two years after the operation, and test results obtained within the first two postoperative years were not considered. Sensory recovery made mainly within the first postoperative year was therefore not assessed.

Evaluation of sensory recovery two years after the operation warrants the con- clusion that an area of hyperpathia*) can always be found, regardless of whether the operative result was very good or very poor. Regardless of a very good recovery, the patient continues to indicate that the area in question ‘feels different’.

The temperature, brush and HP tests in this hyperpathic area were undisturbed in all patients examined. The locognosis test (although performed only once, and not in all patients) seemed normal. This implies that differentiation between a good and a poor operative result on the basis of the above sensibility tests is no longer possible two years after the operation. The differences in operative results did become apparent, however, in the 2PD and the stereognosis test. Tables 4 and 6 show that repeated tests in the same patients give no significantly different results. This implies that a single careful examination with the aid of the 2PD and the stereog- nosis test provides reliable information on these two aspects of functional recovery.

In this context it is to be borne in mind that the use of a wide variety of materials in the stereognosis test made it impossible for the patient to improve the score by recognizing objects previously offered. It is in fact possible to improve the results of

*) Pain Terms. A list with definitions and notes on usage. Pain 1979 Vol. 6, pp. 249-252.

TABLE 5.Survey o

fpat

ient

s

Patie

nt(i

nitia

ls)

A

B

C

D

E

F

Yea

r of

bir

th

1958

19

63

1958

19

63

1925

19

24

Sex

M

M

M

M

M

M

Age

at

acci

dent

17

yea

rs

14 y

ears

16

yea

rs

1 I y

ears

49

yea

rs

50 y

ears

Dia

gnos

is

RM

N*

LM

N

LM

N

RM

N

LM

N

RM

N

Inte

rval

acci

dent

/ope

ratio

n17

mo

3mo

7mo

3mo

5mo

4mo

Gra

ft

leng

th

5 cm

3c

m

7cm

4c

m

5cm

4c

m

Num

ber

of f

asci

culi

5 5

4 5

5 4

*RM

N

= ri

ght

med

ian

nerv

e le

sion

L

MN

=

left

med

ian

nerv

e le

sion

TABLE 6

. E

lect

rom

yogr

aphy

3

year

s af

ter

oper

atio

n __

~_~

_.

..__.

-._-

.___

_. _

. -_

...

~.

A

B

C

D

Med

ian

nerv

e a.

de

nerv

atio

n po

tent

ial’

pr

esen

t no

ne

none

no

ne

b.

mot

or

cond

uctio

n*

dela

yed

abse

nt

dela

yed

dela

yed

c.

sens

ory

cond

uctio

n3

pres

ent

pres

ent

abse

nt

pres

ent

Uln

ar

nerv

e a.

m

otor

co

nduc

tion4

pr

esen

t pr

esen

t pr

esen

t no

t do

ne

b.

sens

ory

cond

uctio

ns

not

done

no

t do

ne

not

done

no

t do

ne

1)

shor

t ab

duct

or

mus

cle

of t

hum

b 2)

st

imul

ated

at

lev

el

of w

rist

an

d de

rive

d fr

om

shor

t ab

duct

or

mus

cle

of t

hum

b 3)

st

imul

ated

fr

om

1st

or 2

nd

fing

er

and

deri

ved

at l

evel

of

wri

st

4)

see

2)

5)

see

3)

--_

._~

~~~.

E

F

none

no

ne

dela

yed

dela

yed

abse

nt

pres

ent

pres

ent

abse

nt

not

done

no

t do

ne

stereognosis tests. This was demonstrated by WYNN PARRY

(1974) who designed a special re-education program for nerve grafting.

99

(1976) and DELLON

patients treated by

In the comparison between the stereognosis test and the 2PD test, it was con- spicious that two patients (C and E) with a good 2PD test had a poor stereognosis test. It was likewise striking that a poor 2PD test did not always imply a poor stereognosis test (A and D). This means that the results of the 2PD test and those of the stereognosis test do not always correlate well.

The difference between the 2PD test and the stereognosis test is that the former is a static and the latter a dynamic test. In the 2PD test the calipers rest on the fingertip. In the stereognosis test the object to be identified moves between the fingers. In the 2PD test the patient is asked to assess the distance between two qualities which as such he can distinguish. The stereognosis test is much more complex, and much closer to the principal sensory function of the hand: recognition of the surrounding world through tactile impulses. MOBERG (1958) described this as ‘seeing’ with the hand. The use of several fingers in the stereognosis test may explain the differences in test result from the 2PD test. The EMG should also be interpreted in this light.

In testing recovery of sensory function two years after nerve transplantation, the stereognosis test should occupy the most prominent position because this test determines the functionally most important aspect of sensibility. The stereognosis test has proved to be simple and readily reproducible.

ACKNOWLEDGEMENT

The authors are indebted to Dr H. Hamburger (Department of Neurology, Slotervaart Hospital, Amsterdam) for his cooperation.

REFERENCES

DELLON. A.L. (1974) Reeducation of sensation in the hand after nerve injury and repair. Plastic. Reconstr.

Surg. 53, 297. HAMBURGER, H.L. (1980) Locognosia Thesis. Amsterdam. MILLESI, H. (1972) The interfascicular nerve grafting of the median and ulnar nerves. Journ. of Bone and

Joint Surg. Vol. 54 A, no. 4 pp., 727. MOBERG, E.L. (1958) Objective methods for determining the functional value of sensibility in the hand. The

Journ. of Bone and Joint Surg. Vol. 40 B, no. 3, pp. 454.

SEDDON, H.J. (1954) Peripheral Nerve Injuries. Medical Research Council Special Report Series no. 282 H.M.S.O., London.

SMITH, J.W. (1964) Microsurgery of peripheral nerves. Plastic. Reconstr.Surg. Vol. 33 pp. 317. WYNN PARRY. C.B. (1976) Sensory re-education after median nerve lesions. The Hand. Vol. 8 no. 3 pp.

250.