Ayub K. Ommaya

TOLERANCES FOR CEREBRAL CONCUSSION FROM HEAD IMPACT AND WHIPLASH IN PRIMATES

Abstract Experimental head impact and whiplash injury experiments have been conducted in 3 sub-human primate species in order to define tolerance thresholds for onset of cerebral concussion. Preliminary analysis of our data support a hypothesis that approximately half of the potential for brain injury during impact to the unprotected movable head is related to head rotation, the remaining brain injury potential of the blow is related to the contact phenomena of the impact. Data derived in these experiments is compared with values predicted from some scaling considerations previously developed. Predictions are made that the levels of head rotation during whiplash, in excess of 1800 rad./sec 2 , will probably result in cerebral concussion in man.

Temporary Occlusion of the Middle Cerebral Artery in the Monkey: Clinical and Pathological Observations

The right middle cerebral artery (MCA) was exposed in monkeys via a retro-orbital microsurgical approach. In 43 animals a temporary occlusive clip was placed on the MCA origin for one to 24 hours. In 20 animals, the origin of the MCA was permanently occluded. Clinical evaluation of the monkeys one to three days postoperatively showed that one to two-hour clipping caused no or mild neurological deficits, four-hour clipping caused mild to moderate deficits, six to eight-hour clipping caused moderate to severe deficits, and 24-hour clipping produced severe deficits or death, a result equivalent to that produced by permanent occlusion. Gross and microscopical evaluation of the brains showed that one to two-hour clipping usually caused no or mild damage, four-hour clipping caused mild to moderate damage (often with capsular sparing), and six to eight-hour clipping and 24-hour clipping produced severe extensive infarction not different from that caused by permanent occlusion. Six to eight-hour clipping and 24-hour clipping were associated with a high incidence of hemorrhagic infarction, but other clipping times were not. The results suggest that reestablishment of flow by surgical means within a few hours after MCA occlusion in selected patients might result in significant restoration of neurological function. If flow renewal were done within about four hours, an increased incidence of hemorrhagic infarction might be avoided.

Selective arteriography of arteriovenous aneurysms of spinal cord.

Myelography is not entirely satisfactory for the preoperative diagnosis of spinal cord vascular malformations. The linear, serpiginous filling defects first described by Guillain and Alajouanine (1) are by no means constant or pathognomonic findings. Lombardi and Migliavacca (2) reported positive myelographic findings in 15 out of 18 spinal angiomas, Teng and Papatheodorou (3) in 6 out of 12 cases, and Verbiest and Calliauw (4) in only 3 of their 12 cases. Iodophendylate (Pantopaque) myelography may also lead to false-positive diagnoses, e.g., vascular malformations in cases of tumor or other lesions with dilated vessels. Nor is gas myelography of any use in the diagnosis of these malformations (5). Prior Investigatioks The diagnostic inadequacies in handling the spinal cord vascular malformations spurred this investigation. We believe, however, that some knowledge of the normal anatomy of the spinal cord vascularization is indispensable for a better understanding of the pathologic anatomy of the lesions....

Mechanical properties of tissues of the nervous system.

Abstract The work presented is a review of the scientific literature pertaining to the mechanical properties of the tissues of the nervous system. Additional articles are reviewed where appropriate to indicate the scope of the total literature pertinent to the subject. Preliminary observations from the authors laboratory are also presented.

A comparison of the elasticity of live, dead, and fixed brain tissue

Abstract The opposition to the intracranial expansion of a thin elastic cylinder in live, dead, and fixed brain tissue has been measured and compared. An analysis of the data, assuming an elastic material, indicates that the elastic modulus increases concavely upward with strain and varies between 1·0 × 103 and 3·5 × 103 dyn/cm2 for the range of strain tested. Death and fixation of brain tissue increases the modulus but does not appear to change the manner in which it varies with strain.

SCALING OF EXPERIMENTAL DATA ON CEREBRAL CONCUSSION IN SUB-HUMAN PRIMATES TO CONCUSSION THRESHOLD FOR MAN

Abstract : A method of extending the results of experiments on concussion-producing head rotations on lower primate subjects to predict the rotations required to produce concussions in man is presented. A rational scheme of development of the overall investigation is outlined. Theoretical scaling factors are derived and discussed and the results of concussion-producing tests on the Rhesus monkey are presented in chart form. A chart of angular acceleration required to produce concussion in the Rhesus monkey indicates that an acceleration of 40,000 radians per second sq will have a >99 percent probability of producing concussion. The scaling factors presented herein tentatively indicate that an acceleration of 7,500 radians per second sq will have the same probability of producing concussion in man.

Cerebrospinal fluid perfusion for central nervous system neoplasms

CENTHAL NERVOUS system neoplasms have long defied effective treatment.1-4 The functional anatomy has limited the surgical approach.2,4,5 The unique physiology and microscopic anatomy implied in the concept of a “blood-brain barrier,” limits the entrance of many chemotherapeutic agents from blood to brain+-s and, by so doing, makes systemic chemotherapy inadequate.9 Local arterial perfusion, which is promising in some anatomical sites, does not circumvent the “blood-brain barrier” and is in addition fraught with prohibitive toxicity.10-12 The unique anatomy, physiology, and pharniacology of the central nervous system can, however, be beneficially utilized and their previously frustrating limitations advantageously applied. It has been shown recently that lipid insoluble and highly ionized organic moleculeslx can pass, by diffusion, from cerebrospinal fluid to brain,GJ4Jb while the “bloodbrain barrier” limits movement of such substances in the opposite direction, that is, from brain to blood. Accordingly, a system was devised utilizing cerebrospinal fluid pathways for the continuous and restricted delivery of high concentrations of chemotherapeutic agents from ventricular and spinal fluid to brain.l(;J7 The great disparity in deoxyribonucleic acid (DNA) metabolism between normal brain and malignant tissue should make these tumors an ideal target for chemotherapeutic agents.lx-’O

Prognostic criteria for cerebrospinal fluid shunting from isotope cisternography in communicating hydrocephalus

IT IS WELL ESTABLISHED that ventricular filliiig in radioisotope cisternography provides reliable evidence of communicating hydro~ephalus.l-~ Numerous reports have shown that surgical shunting is highly beneficial in certain cases of adult communicating hydrocephalu~,5--~ although the prognostic criteria for surgical success have not been defined. Because of the need to avoid unnecessary and potentially hazardous surgery in patients with little likelihood of improvement, increased diagnostic accuracy is desirable. In reviewing the radioisotope cisternograms of patients with communicating hydrocephalus, we found poor correlation between ventricular filling alone and favorable response to shunting. However, where there was prolonged ventricular retention of the isotope, shunting proved successful in nearly every case. This suggests that cistemography possesses significant prognostic value in communicating hydrocephalus and may influence surgical decisions.

Value of cutaneous angiomas in the arteriographic localization of spinal-cord arteriovenous malformations.

Abstract A careful search for segmentally related cutaneous hemangiomas in a series of 28 patients with spinal-cord arteriovenous malformations revealed six with such an association, a much higher prevalence than previously reported. Close scrutiny of the back is required to detect these often minor skin changes. Selective arteriography demonstrated opacification of both the spinal and the cutaneous vascular malformation from the same intercostal or lumbar artery, confirming the similar metameric origin of both lesions. Recognition of the skin lesion in a patient with obscure spinal-cord symptoms is important both as a clue to the etiology of the myelopathy and as an aid in the localization of arterial feeders to the spinal malformation before surgery.

Granulomatous angiitis of the brain A successfully treated case

A patient with clinical and radiographic findings initially suggesting a neoplasm was diagnosed as having Hodqkin disease. Computerized axial tomography demonstrated profound diffuse decreased density similar to that seen in cases of cerebral edema or leukomalacia. Cerebral angiography showed blood vessels with a beaded appearance. A diagnosis of granulomatous angiitis was made on the basis of brain biopsy specimens. Viral cultures were negative. Skin testing revealed poor responses to antigens. The patient improved dramatically following a combination of radiotherapy and steroid therapy. Resolution of the low-density abnormality seen on serial EMI scanning and resolution of the vasculitis demonstrated in the post-therapy brain biopsy specimen was dramatic. This is the first case of granulomatous angiitis of the brain diagnosed during life, and it points out the value of radiation and steroid therapy for relief of neurologic symptoms.