A. K. - IRCOBI · 803, 1971. 13. Gennarelli, T., Thibault, L. and Ommaya, A.K.: Pathophysiologie ... Ommaya, A.K. et al: Traumatic unconsciousness: Mechanisms of Brain

HEAD AND SPINAL INJURY TOLERANCE WITH NO DIRECT HEAD IMPACT

By

A. K. Ommaya, M . D . , F . R . C . S . and L. Thibault

This paper reviews the s tate of the art concerning tolerance for

injury to the central nervous sys tem when the head is not directly s truck.

Progress in this area of the biokinetics of impact has been hampered by

the diff iculty of sustained collaborative work in the three f ields which

must be coordinated in order to achieve adequate reliability o f data ;

namely, mathemat ical mode l s , experimental work with physical and animal

models and predictive val idation from human accident data .

After reviewing the four analytic models currently availab l e , this

paper wil l summarize the current knowledge concerning the o ther two areas

mentioned with special reference to experimental work conducted by the

author a t the National Inst itutes of Health.

M athema tical Mod e l s

1 . ADVANI . This mod e l i s of an elastic spherical she l l with a low

modulus elastic/visco-elastic core , subj ected to three types of loading :

1 . axisymmetric translational impact

2 . symmetric torsional impact

3 . whiplash type loading

The model drives numerical s o lutions for limiting desplacements , shear ,

and normal s tresses .

2 . HAYASHI . This i s a two dimensional model , consisting of elastic-

ally connected concentric r igid body cylinder s . The loading i s in the

sagittal p lane symmetry with angular acceleracion v s . t ime for the real

3 1 1

, , S ituation replaced by pulse wave eMAX for equivalent time duration tD .

The model derives resul tant shear Stress vs . eMAX tD and uses the

,

constitut ive relations to determine the critical level s for inj ury . The

data derived from this model was compared to our experimental data with

reasonabl e correspondence.

3. JOSEPH AND CRI SP . This model is of a spheroidal brain-skull

body having the mathema tical relat ionship x2 + 7 The loading used in this model was a cons tant angular velocity i . e . , a

s t eady rotational motion about any of 3 mutually orthogonal axe s . The

model derives expressions for mechanical s tresses , s trains and disp lace-

ments of the brain and uses the constitutive relations developed by

the data from the work of Galford and McElhaney.

4 . BYCROFT . This model is of the skull as a rigid spherical she l l

and of the brain a s a s impl e elastic solid . The loading is a full sine

and half-sine angular acceleration in the axisymmetric plane and it

derives expres s ions for shear s tress as a complex function of time and

radial posi tion in the mod e l . Holburn ' s sca l ing law is used and compared

to data obta ined from some of this authors experimenta l work

Experimental Work in the Rhesus Animal Mode l .

Two hypotheses which have s t imulated considerable research in the

field of head inj uries are a ssociated with the name of Holbourn and

Gurdj ian. Based on experiments with gelatin models of the brain

Holbourn believed that rotational components of inert ia l loading of

the head was the mos t s ignificant cause of diffuse effects on the

brain (e . g . cerebral concussion and contrecoup lesions ) . He dis­

counted translational component s of inertia l loading claiming that the

resultant compre s s ion or rarefaction of the brain would not be s igni­

ficantly inj uriou s . ( l , 2 ) Gurdj ian correctly pointed out that this

analysis neglected the effect o f the foramen magnum and the work of

this inves t igator and his colleagues over the past 25 years a t Wayne

S tate University has formed the basis o f the current standard tolerance

curve for head injury used by design engineers the world ove r . ( 3 , 4 )

Because this curve i s expressed i n terms o f translational acceleration

only it was impor tant to determine experimentally the precise individual

contribution of both translation and ro tation to the injury potential of

inert ial loading of the brain. Both hypothesi s accept that the contact

phenomena of impac t are the main cause of focal lesions at or near the

site of impact but differ on the relative s ignificance of the transla tional

and rotational component of inertial loading caused by impact . Our earlier

work had shown that pure inert ial loading produced by experimental whiplash

could produce cerebral concussion and surface haemorrhages of the brain

(primarily subarachnoid and subdural b leeding ) . < 5 , 6 ) Although the traumatic

unconsciousness thus produced by a combination o f head rotation and trans­

la tion without direct impact was identical to that seen after head impac t ,

the l esions found in the brain differed in the two types o f inj ury . This

difference was primarily due to the presence of cerebral contusions , no t

explicable solely by the contact phenomena of impact . ( 7 )

This part o f the paper presents our current data obtained b y two new

techniques ; firstly the use of a special head holding device has a llowed us

to compare for the first time the inj urious effects of pure translational

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acceleration of the head with head rotation at equivalent level s of input

acceleration and without the complicating effect of impact contac t

phenomena . (See Figure 1) Secondly, we have developed the somatosensory

evoked response (SER) as an in-vivo index of the onset and duration of

traumatic uncons c iousnes s and development of brain lesions . (See Figure 2)

We have evidence that cerebral concussion and diffuse lesions in the brain

are caused primarily by the rotational component of inertial loading while

cortical contusions , intracerebral haematomas and s imilar focal lesions

are primarily due to translation . (See Figure 3 ) At the levels of

acceleration tested , cerebral concussion was invariably produced by rotation

but no t by translation of the head . ( B , 9 ) These data will b e presented and

d iscussed . Implications of these data .

1 . The standard tolerance curve for head injury wil l have to be modified

to take into account the role of rotation .

2 . With this model for clo sed head injury it is pos s ible to test hypotheses

for head inj ury mechanisms with precision and ease .

3 . lt i s now possible to analyse the c l inical phenomena of head inj ury (coma ,

amnesia and post-traumat ic sequelae) in a reproducible primate mode l .

4 . Our work to date makes i t poss ible to re-define cerebral concuss ion in a

way such that the clinical and experimental data are reconciled . This

hypothes i s will be discussed .

5 . The technique o f SER recording i s directly applicable to man for the

development of an ' on-line ' in-vivo index of severity of head injury a s

well a s a research tool to unravel the mechanisms of neural trauma in

the human .

Results With A Phys ical Model Using The Technique Of Moire Analysi s O f Strain.

In collaboration with Dr . A. J . Durelli o f Catholic University , we are

currently performing experiments on four hal f skull s o f the squirrel monkey ,

rhesus monkey , chimpanzee and the human . These half sku l l s are f illed with

a s ilicon material with physical properties approaching that of brain on

which a grating has been printed and the entire surface i s covered with a

lexan plate . These models are subj ected to linear and rotational acceler­

ations and the Moire pat terns of the resulant deformation are analyized to

determine the relative displacement o f points in the plane o f symmetry of

the brain mode l . This wil l be the f ir s t s tep in the determinat ion o f

strains , velocities , and accelerations t o which each point is subj ected in

the proce s s of indirect impac t . Prel iminary resul t s of these experiments

sha l l also be reviewed in this paper . Finally the paper wil l at tempt to

correlate the available human injury data in this type of injury s ituation

with the current available data from the models and possible directions

for future work will be outlined .

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Bibl iography

1 . Advani , S . H . , Owings , R . P . and Schuck, L . Z . : Response Evaluation of Translational and Rotational Head Injury Models . Shock and Vibration Digest . October , 1 9 7 2

2 . Hayashi , Tsuyoshi . Brain Shear Theory of Head Injury due to Rota­t ional Impac t . Journal of the Faculty of Engineering. U. Tokyo . (B) . Val . 3 0 , No . 4 . 1 9 7 0 .

3 . Joseph, P . D . and Crisp , J .D . C . : On the evaluation of Mechanical Stresses in the Human Brain while in motion . Brain Research . Val . 26 15-3 5 , 1 9 7 2 .

4 . Bycrof t , G . N . : Acceleration .

Mathematical Model of a Head subj ected to Angular In press (Journal o f Biomechanics) .

5 . Holbourn, A . H . S . : Mechanics o f Head Injuries . Lancet 2 : 438 . 1943 .

6 . Holbourn , A . H . S . : Mechanics of Brain Inj ur ie s . British Medical Bulletin 3 : 1 4 7 , 1 945 .

7 . Gurdj ian , E . S . , Lissner , H . R . , Hodgson, V . R . et a l : Mechanisms of Head Inj ury . Clinical Neurosurgery 12 : 1 1 2 , 1966 .

8 . Gurdj ian, E . S . , Rober t s , V . L . and Thomas , L .M . : Tolerance curves of acceleration and intracranial pressure and protec tive index in experimental head inj ury . Journal Trauma 6 : 600-604 , 1966 .

9 . Ommaya , A . K . , Hirsch, A . E . and Martinez , J . : The role of "whiplash" in cerebral concussion. Proceedings of lOth S tapp Car Crash Conf­erenc e , 197-203 , 1966 .

1 0 . Ommaya , A . K . , Faas , F . and Yarne l l , P . : Whiplash injury and brain damage : An experimental study . JAMA 204 : 285-28 9 , 1968 .

1 1 . Ommaya , A . K . , Brugg , R . L . and Naumann, R . A . : Coup and contre-coup inJ ury : observations on the mechanics of visible brain injuries in the rhesus monkey . J . Neurosurgery 35 : 503-516 , 1971 .

1 2 . Gennare l li , T . , Thibaul t , L . and Ommaya , A . K . : Comparison of translational and rotational head motions in experimental cerebral concussion . Proceedings of 15th Stapp Car Crash Conference , 797-803, 1 9 71 .

13 . Gennarell i , T . , Thibault , L . and Ommaya , A . K . : Pathophysiologie responses to rotat ional and translational acceleration of the head . Proceedings of 16th S tapp Car Crash Conferenc e , 296-308 , 1972 .

14 . Ommaya , A . K . et al : Traumatic unconsciousne s s : Mechanisms of Brain Injury in violent shaking of the head . Proceedings American Assoc . Neurological Surgeons . Paper No . 3 6 , 1973 .

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