- Email: [email protected]
Prolonged survival after severe traumatic injury limited to the brainstem
Surg Neurol 1985;23:525-8
525
Prolonged Survival after Severe Traumatic Injury Limited to the Brainstem R. C. Kim, M.D., K. Fagin, M.D., and B. H. Choi, M.D. The Laboratory Service, Veterans Administration Medical Center, Long Beach, California, and the Departments of Pathology and Neurosurgery, University of California, Irvine, California College of Medicine, Irvine, California
Kim RC, Fagin K, Choi BH. Prolonged survival after severe traumatic injury limited to the brainstem. Surg Neurol 1985;23:525-8.
It has been suggested that primary traumatic lesions of the brainstem do not occur in the absence of widespread injury to other parts of the brain. We describe a patient who suffered a severe head injury that left him with paralysis of three extremities and weakness in the fourth. Intellectual function was entirely preserved. Neuropathological examination 39 years after the injury disclosed the presence of a cavitary lesion within the basis pontis. There was no pathological evidence of traumatic injury to any other part of the central nervous system. KEY WORDS" Head trauma; Brainstem; Locked-in syndrome; Retrograde degeneration; Corticospinal tract
Although it is known that primary damage to the brainstem may follow blunt head injuries, it is widely believed that, with the possible exception of the hyperextensioninduced pontomedullary rent [8,12,16], such damage is virtually always accompanied by widespread lesions at other sites, particularly in the cerebral white matter and corpus callosum [2-4,13,14,16,19], and that it is generally incompatible with prolonged survival. In this report we describe a patient who became severely disabled neurologically after a primary traumatic lesion of the basis pontis and who, at autopsy 39 years later, showed no pathologic evidence of traumatic damage to any other part of the central nervous system. Case Report In 1943, at the age of 25, the patient was shot down in the B-17 bomber that he was piloting. By the patient's own description, though unconscious initially, he awak-
Address reprint requests to: Ronald C. Kim, M.D., Laboratory Service (113), VA Medical Center, 5901 East 7th Street, Long Beach, California 90822. © 1985 by Elsevier Science PublishingCo., Inc.
ened a few days later unable to move his arms or legs or to make any sounds. H e remained in this state for approximately 6 months, after which speech and motor function improved gradually over a period of about 6 years; thereafter, his neurological condition remained stable. H e was fully oriented and his intellect was judged to be completely intact. Speech was spastic, monotonous, and markedly dysarthric. H e could understand everything that was said to him and could read and write without difficulty. Visual acuity was approximately 20/100. T h e visual fields were full to confrontation. The pupils were round and reactive to light until bilateral peripheral iridectomies were performed for glaucoma in 1972, after which they became irregular and only minimally reactive. There was full range of motion of the extraocular muscles without diplopia or nystagmus. Mastication and facial sensation were normal. Other abnormalities of cranial nerve function included the following: right central facial weakness; bilateral sensorineural hearing loss, most pronounced at higher frequencies; absent gag reflex, associated with difficulty swallowing liquids; atrophy of the shoulder girdles; loss of sternocleidomastoid function on the left; and weak tongue protrusion, with deviation to the right (although neither atrophy nor fasciculations were noted). Both lower extremities and the right upper extremity were paralyzed and hyperreflexic. H e was, however, able to raise and lower the left arm; although the grip on that side was weak, there was sufficient strength in the wrist and intrinsic hand muscles to enable him to write and to type on a special typewriter. N o Babinski responses were elicited. All modalities o f sensation, including light touch, pinprick, vibration, and position perception, were intact. Rectal tone was judged to be fair, with some preservation of bowel and bladder sphincter control. Roentgenograms of the skull, 99'~Tc brain scan, echoencephalogram, and electroencephalogram, all of which were performed in 1973, were judged to be normal. Computed tomography scans o f the brain and skull were never performed. Other medical problems included adult-onset diabetes mellitus, anteroseptal myocardial infarction, and recurrent urinary tract infections. During the latter years 0090-3019/85/$3.30
526
Surg Neurol 1985;23:525-8
of his life he resided in a nursing home and became doubly incontinent. He was still able, however, to move about in an electric wheelchair. In 1982, at the age of 64, he was hospitalized for fever, lethargy, and hypotension. He was treated with antibiotics but suffered a cardiopulmonary arrest, after which, though breathing spontaneously, he was comatose. Examination by a neurologist showed him to be unresponsive to verbal or noxious stimuli, with minimal corneal, absent doll's-head eye, and normal caloric responses. He died shortly thereafter, some 39 years after his injury. Although there was no indication in the hospital records that he had, during the last 20 years of his life, undergone extensive psychometric evaluation, the presence of a large volume of correspondence from the patient to various members of the hospital and administrative staff strongly indicates that his intellect had been well preserved. According to his widow, this correspondence had been undertaken without assistance, typewritten, and signed by his own hand. The letters, which were often quite lengthy, were carefully written and well articulated, and expressed in considerable detail many of the problems he claimed to have encountered, such as the discomfort he had experienced while having blood drawn, the alleged indifference of some of the physicians who had attended him, problems with billing, difficulty in obtaining prescription sunglasses, a desire to obtain in-home aid and attendance during emergencies, and the shortage of hospital parking spaces for handicapped outpatients. There was a clear indication that he had known the names of most if not all of the physicians that he had encountered, that he had been thoroughly familiar with many of the commercially available appliances and accessories for handicapped individuals, and that he had read and understood most of the federal and state regulations pertaining to disabled veterans.
Kim et al
Figure 1. Coronal section of the cerebral hemispheres. Note the normal appearance o/the white matter and lateral ventricles. (The cleft in the white matter on the left side is an~artifact.) hippocampal gyri. In horizontal secuon, the basis pontis contained an irregular, multiloculated cavitary lesion measuring 0.9 cm in maximum diameter, which extended rostrocaudally for a distance of about 0.6 cm, from the upper end of the fourth ventricle downward almost to the level at which the trlgeminal nerve roots emerged (Figure 2). Rostrally the lesion occupied the dorsal two-thirds of the basis pontis, extending 0.4-0.5 cm from the midline on either side; caudally, however, it was confined to the left side. Both transverse pontocerebellar and descending corticospinal fibers appeared to have been breached, especially dorsally. There were shrinkage and greyish discoloration of the medullary pyramids. The cerebral arteries, including the basilar artery, were widely patent and free of atherosclerosis. The spinal cord was grossly normal except for pallor in the vicinity of the lateral corticospinal tracts.
Pathological Findings The principal general autopsy findings were severe chronic pyelonephritis, with nephrolithiasis and hydronephrosis, and extensive old myocardial infarction. There was no evidence of fracture, either of the calvarium or of the base of the skull. The spinal canal was smooth and unobstructed. The brain was fixed in formalin, and weighed 1580 g. Externally and in coronal section, the cerebral hemispheres were of normal gross appearance; the white matter was normal in color and consistency, and the basal ganglia, thalamus, and ventricular system were normal in size and configuration (Figure 1). No old loci of pressure necrosis were identified in the cingulate or para-
Figure 2. Horizontal sections of the pons. There is an irregular, multiloculated cavitary lesion within the basis pontis.
Traumatic Brainstem Injury
Microscopically, there was widespread acute hypoxic brain damage, as evidenced by the presence of ischemic cell change and early microglial activation within the cerebral cortex, hippocampus, basal ganglia, thalamus, and cerebellar cortex. Examination of many blocks of cerebral tissue, especially of the white matter and corpus callosum, failed to reveal evidence of chronic injury in the form of microglial stars, foci of pallor of myelin staining, or axonal retraction balls. The irregular, multiloculated cavitary lesion noted grossly within the basis pontis, which contained only a rare macrophage, was traversed by slender strands of gliovascular tissue and bordered by a zone of pallor and rarefaction showing severe loss of myelinated fibers, a few residual swollen axons, and reactive gliosis. Where the cross-sectional extent of the lesion was greatest, many of the descending corticospinal and transversely oriented pontocerebellar fibers appeared to have been interrupted on either side (Figure 3). The staining density of the myelin within the middle cerebellar peduncles, however, was only minimally reduced. Dorsally, cavitation extended into the ventromedial left medial lemniscus. Above the lesion there was a moderate loss of myelinated fibers within the corticospinal tracts; pallor of myelin staining, which was somewhat more pro-
Figure 3. Photomicrograph of the rostral midpons. The lesion interrupts
both descending corticospinal and transverse pontocerebellarfibers. Dorsally, it extends into the left medial lemniscus (Kliiver-Barrera: x 4.9).
Surg Neurol 1985;23:525-8
527
nounced on the left, was noted within the middle third of the cerebral peduncle (Figure 4) and in the caudal portion of the posterior limb of the internal capsule on either side, but could not be followed any farther rostrally. Below the pontine lesion there was wallerian degeneration of the corticospinal tracts. Within the medullary pyramids there was a nearly total loss of myelinated fibers, except for an area of relative sparing laterally on the right. Within the spinal cord there was severe loss of myelinated fibers from the lateral corticospinal tracts on both sides and from the uncrossed (ventral) corticospinal tract on the left. No histologic abnormalities were noted within the basilar artery or the pituitary gland. Discussion To our knowledge, the course of illness described in this patient represents the longest period of survival ever recorded after severe, pathologically documented primary traumatic injury to the brainstem. Although there are a few reports in the literature of relatively long sur-
Figure 4. Photomicrograph of the caudal midbrain. Note the pallor of staining of those portions of the cerebralpeduncles occupied by descending corticospinal fibers (arrows) (Kliiver-Barrera: x 4.7L
528
Surg Neurol 1985;23:525-8
vival after autopsy-confirmed primary brainstem injury of comparable severity [10,18,19], these cases differ from the one presented here in two major respects: (a) clinically, there was marked impairment of intellectual function or level of consciousness, and (b) pathologically, there was evidence of widespread brain damage. The location and extent of the lesion within the basis pontis account for the patient's transitory "locked-in" state and for all of the residual neurologic deficits. Preservation of intellect and the relative sparing of function in the left upper extremity undoubtedly contributed to his unusually long survival. That the brainstem lesion was of primary rather than of secondary nature is indicated by its ventral and caudal location within the pons, by the absence of any longstanding structural abnormalities above the tentorium, and by the absence of any old foci of pressure necrosis within the cingulate or parahippocampal gyri [ 1,6,17,18 ]. In accordance with the suggestion made by others [ 1,17,18], we believe that primary traumatic lesions within the basis pontis, such as the one we have described here, are most probably the result of shearing of axons at the moment of impact. We think it unlikely, on the basis of its pathologic appearance, that a hematoma had developed at the site of injury. Traumatic vascular occlusion also is not likely to have been responsible, in view of the histopathologically normal appearance of the basilar artery. The presence of retrograde degeneration within the corticospinal tracts confirms the observations of others [5,7,9,11] in both human and animal material. Whether there is a loss of Betz cells or merely a reduction in their volume after transection of the pyramidal tracts, however, is a matter of considerable debate [7,11]. In this instance, examination of many sections of motor cortex suggested a considerable reduction in the concentration of Betz cells on either side, although no attempt at quantitative analysis was made, largely because of the presence of widespread ischemic cell change. Particularly noteworthy is our failure to find evidence of widespread injury (in the form of microglial stars, axonal retraction balls, or ventricular enlargement) at other sites within the central nervous system. Many investigators have emphasized the great rarity with which the brainstem is affected in the absence of cerebral hemispheric injury after blunt trauma [2-4, 13,14,16,19]; indeed, the view has been expressed that, except for the pontomedullary rent that may develop after a hyperextension injury, primary traumatic brainstem lesions do not occur in isolation [2-4,13]. The findings in the case that forms the basis of this report, however, clearly establish that severe primary brainstem injury may occur in the absence of diffuse cerebral damage, and that the
Kim et al
possibility of such an occurrence, though rare, must be borne in mind when dealing with the head-injured patient. This study was supported in part by Grant ES 02928 from the National Institute of Environmental Health Sciences.
References 1. Adams H, Graham DI. The pathology of blunt head injuries. In: Critchley M, O'Leary JL, Jennett B, eds. Scientific foundations of neurology. Philadelphia: PA Davis, 1972:478-91. 2. Adams JH. The neuropathology of head injuries. In: Vinken PJ, Bruyn GW, Braakman R, eds. Handbook of clinical neurology, Vol 23. Amsterdam: North-Holland, 1975:35-65. 3. Adams JH, Gennarelli TA, Graham DI. Brain damage in nonmissile head injury: observations in man and subhuman primates. In: Smith WT, Cavanagh JB, eds. Recent advances in neuropathology, No. 2. Edinburgh: Churchill Livingstone, 1982:165-90. 4. Adams JH, Mitchell DE, Graham DI, Doyle D. Diffuse brain damage of immediate impact type: its relationship to 'primary brain-stem damage' in head injury. Brain 1977;100:489-502. 5. Bronson R, Gilles FH, Hall J, Hedley-White ET. Long-term posttraumatic retrograde corticospinal degeneration in man. Hum Pathol 1978;9:602-7. 6. Crompton MR. Brainstem lesions due to closed head injury. Lancet 1971:669-73. 7. Feringa ER, Vahlsing HL, Smith BE. Retrograde transport in corticospinal neurons after spinal cord transection. Neurology 1983;33:478-82. 8. Harding B, Erdohazi M. Traumatic transection of the brainstem. J Neurol Neurosurg Psychiatry 1981;444:1156-8. 9. Holmes G, May WP. On the exact origin of the pyramidal tracts in man and other animals. Brain 1909;32:1-43. 10. Huhn B, Jakob H. Traumatische Hirnstamml~isionen mit vielj~ihriger Uberlebensdauer. Beitrag zur Pathologie der Substantia nigra und der oralen Briickenhaube. Nervenarzt 1970;41:326-34. 11. Kalil K, Schneider GE. Retrograde cortical and axonal changes following lesions of the pyramidal tract. Brain Res 1975;89:15-27. 12. Lindenberg R, Freytag E. Brainstem lesions characteristic of traumatic hyperextension of the head. Arch Pathol 1970;90:509- l 5. 13. Mitchell DE, Adams JH. Primary focal impact damage to the brainstem in blunt head injuries: does it exist? Lancet 1973;ii:215-8. 14. Ommaya AK, Gennarelli TA. Cerebral concussion and traumatic unconsciousness: correlation of experimental and clinical observations on blunt head injuries. Brain 1974;97:633-54. 15. Pilz P, Strohecker J, Brobovschek M. Survival after traumatic ponto-medullary tear. J Neurol Neurosurg Psychiatry 1982; 45:422-7. 16. Rosenblum WI, Greenberg RP, SeeligJM, Becker DP. Midbrain lesions: frequent and significant prognostic feature in closed head injury. Neurosurgery 1981;9:613-20. 17. Strich SJ. Shearing of nerve fibres as a cause of brain damage due to head injury: a pathological study of twenty cases. Lancet 1961;ii:443-8. 18. Tomlinson BE. Brain-stem lesions after head injury. J Clin Pathol 1970;23(Suppl 4): 154-65. 19. Zolt~in L. Clinico-pathological changes in cases of traumatic brain stem lesions with long survival. In: De Vet AC, ed. Proceedings of the Third International Congress of Neurological Surgery, Copenhagen, 1965. International Congress Series No 110. Amsterdam: Excerpta Medica, 1966:151-6.
525
Prolonged Survival after Severe Traumatic Injury Limited to the Brainstem R. C. Kim, M.D., K. Fagin, M.D., and B. H. Choi, M.D. The Laboratory Service, Veterans Administration Medical Center, Long Beach, California, and the Departments of Pathology and Neurosurgery, University of California, Irvine, California College of Medicine, Irvine, California
Kim RC, Fagin K, Choi BH. Prolonged survival after severe traumatic injury limited to the brainstem. Surg Neurol 1985;23:525-8.
It has been suggested that primary traumatic lesions of the brainstem do not occur in the absence of widespread injury to other parts of the brain. We describe a patient who suffered a severe head injury that left him with paralysis of three extremities and weakness in the fourth. Intellectual function was entirely preserved. Neuropathological examination 39 years after the injury disclosed the presence of a cavitary lesion within the basis pontis. There was no pathological evidence of traumatic injury to any other part of the central nervous system. KEY WORDS" Head trauma; Brainstem; Locked-in syndrome; Retrograde degeneration; Corticospinal tract
Although it is known that primary damage to the brainstem may follow blunt head injuries, it is widely believed that, with the possible exception of the hyperextensioninduced pontomedullary rent [8,12,16], such damage is virtually always accompanied by widespread lesions at other sites, particularly in the cerebral white matter and corpus callosum [2-4,13,14,16,19], and that it is generally incompatible with prolonged survival. In this report we describe a patient who became severely disabled neurologically after a primary traumatic lesion of the basis pontis and who, at autopsy 39 years later, showed no pathologic evidence of traumatic damage to any other part of the central nervous system. Case Report In 1943, at the age of 25, the patient was shot down in the B-17 bomber that he was piloting. By the patient's own description, though unconscious initially, he awak-
Address reprint requests to: Ronald C. Kim, M.D., Laboratory Service (113), VA Medical Center, 5901 East 7th Street, Long Beach, California 90822. © 1985 by Elsevier Science PublishingCo., Inc.
ened a few days later unable to move his arms or legs or to make any sounds. H e remained in this state for approximately 6 months, after which speech and motor function improved gradually over a period of about 6 years; thereafter, his neurological condition remained stable. H e was fully oriented and his intellect was judged to be completely intact. Speech was spastic, monotonous, and markedly dysarthric. H e could understand everything that was said to him and could read and write without difficulty. Visual acuity was approximately 20/100. T h e visual fields were full to confrontation. The pupils were round and reactive to light until bilateral peripheral iridectomies were performed for glaucoma in 1972, after which they became irregular and only minimally reactive. There was full range of motion of the extraocular muscles without diplopia or nystagmus. Mastication and facial sensation were normal. Other abnormalities of cranial nerve function included the following: right central facial weakness; bilateral sensorineural hearing loss, most pronounced at higher frequencies; absent gag reflex, associated with difficulty swallowing liquids; atrophy of the shoulder girdles; loss of sternocleidomastoid function on the left; and weak tongue protrusion, with deviation to the right (although neither atrophy nor fasciculations were noted). Both lower extremities and the right upper extremity were paralyzed and hyperreflexic. H e was, however, able to raise and lower the left arm; although the grip on that side was weak, there was sufficient strength in the wrist and intrinsic hand muscles to enable him to write and to type on a special typewriter. N o Babinski responses were elicited. All modalities o f sensation, including light touch, pinprick, vibration, and position perception, were intact. Rectal tone was judged to be fair, with some preservation of bowel and bladder sphincter control. Roentgenograms of the skull, 99'~Tc brain scan, echoencephalogram, and electroencephalogram, all of which were performed in 1973, were judged to be normal. Computed tomography scans o f the brain and skull were never performed. Other medical problems included adult-onset diabetes mellitus, anteroseptal myocardial infarction, and recurrent urinary tract infections. During the latter years 0090-3019/85/$3.30
526
Surg Neurol 1985;23:525-8
of his life he resided in a nursing home and became doubly incontinent. He was still able, however, to move about in an electric wheelchair. In 1982, at the age of 64, he was hospitalized for fever, lethargy, and hypotension. He was treated with antibiotics but suffered a cardiopulmonary arrest, after which, though breathing spontaneously, he was comatose. Examination by a neurologist showed him to be unresponsive to verbal or noxious stimuli, with minimal corneal, absent doll's-head eye, and normal caloric responses. He died shortly thereafter, some 39 years after his injury. Although there was no indication in the hospital records that he had, during the last 20 years of his life, undergone extensive psychometric evaluation, the presence of a large volume of correspondence from the patient to various members of the hospital and administrative staff strongly indicates that his intellect had been well preserved. According to his widow, this correspondence had been undertaken without assistance, typewritten, and signed by his own hand. The letters, which were often quite lengthy, were carefully written and well articulated, and expressed in considerable detail many of the problems he claimed to have encountered, such as the discomfort he had experienced while having blood drawn, the alleged indifference of some of the physicians who had attended him, problems with billing, difficulty in obtaining prescription sunglasses, a desire to obtain in-home aid and attendance during emergencies, and the shortage of hospital parking spaces for handicapped outpatients. There was a clear indication that he had known the names of most if not all of the physicians that he had encountered, that he had been thoroughly familiar with many of the commercially available appliances and accessories for handicapped individuals, and that he had read and understood most of the federal and state regulations pertaining to disabled veterans.
Kim et al
Figure 1. Coronal section of the cerebral hemispheres. Note the normal appearance o/the white matter and lateral ventricles. (The cleft in the white matter on the left side is an~artifact.) hippocampal gyri. In horizontal secuon, the basis pontis contained an irregular, multiloculated cavitary lesion measuring 0.9 cm in maximum diameter, which extended rostrocaudally for a distance of about 0.6 cm, from the upper end of the fourth ventricle downward almost to the level at which the trlgeminal nerve roots emerged (Figure 2). Rostrally the lesion occupied the dorsal two-thirds of the basis pontis, extending 0.4-0.5 cm from the midline on either side; caudally, however, it was confined to the left side. Both transverse pontocerebellar and descending corticospinal fibers appeared to have been breached, especially dorsally. There were shrinkage and greyish discoloration of the medullary pyramids. The cerebral arteries, including the basilar artery, were widely patent and free of atherosclerosis. The spinal cord was grossly normal except for pallor in the vicinity of the lateral corticospinal tracts.
Pathological Findings The principal general autopsy findings were severe chronic pyelonephritis, with nephrolithiasis and hydronephrosis, and extensive old myocardial infarction. There was no evidence of fracture, either of the calvarium or of the base of the skull. The spinal canal was smooth and unobstructed. The brain was fixed in formalin, and weighed 1580 g. Externally and in coronal section, the cerebral hemispheres were of normal gross appearance; the white matter was normal in color and consistency, and the basal ganglia, thalamus, and ventricular system were normal in size and configuration (Figure 1). No old loci of pressure necrosis were identified in the cingulate or para-
Figure 2. Horizontal sections of the pons. There is an irregular, multiloculated cavitary lesion within the basis pontis.
Traumatic Brainstem Injury
Microscopically, there was widespread acute hypoxic brain damage, as evidenced by the presence of ischemic cell change and early microglial activation within the cerebral cortex, hippocampus, basal ganglia, thalamus, and cerebellar cortex. Examination of many blocks of cerebral tissue, especially of the white matter and corpus callosum, failed to reveal evidence of chronic injury in the form of microglial stars, foci of pallor of myelin staining, or axonal retraction balls. The irregular, multiloculated cavitary lesion noted grossly within the basis pontis, which contained only a rare macrophage, was traversed by slender strands of gliovascular tissue and bordered by a zone of pallor and rarefaction showing severe loss of myelinated fibers, a few residual swollen axons, and reactive gliosis. Where the cross-sectional extent of the lesion was greatest, many of the descending corticospinal and transversely oriented pontocerebellar fibers appeared to have been interrupted on either side (Figure 3). The staining density of the myelin within the middle cerebellar peduncles, however, was only minimally reduced. Dorsally, cavitation extended into the ventromedial left medial lemniscus. Above the lesion there was a moderate loss of myelinated fibers within the corticospinal tracts; pallor of myelin staining, which was somewhat more pro-
Figure 3. Photomicrograph of the rostral midpons. The lesion interrupts
both descending corticospinal and transverse pontocerebellarfibers. Dorsally, it extends into the left medial lemniscus (Kliiver-Barrera: x 4.9).
Surg Neurol 1985;23:525-8
527
nounced on the left, was noted within the middle third of the cerebral peduncle (Figure 4) and in the caudal portion of the posterior limb of the internal capsule on either side, but could not be followed any farther rostrally. Below the pontine lesion there was wallerian degeneration of the corticospinal tracts. Within the medullary pyramids there was a nearly total loss of myelinated fibers, except for an area of relative sparing laterally on the right. Within the spinal cord there was severe loss of myelinated fibers from the lateral corticospinal tracts on both sides and from the uncrossed (ventral) corticospinal tract on the left. No histologic abnormalities were noted within the basilar artery or the pituitary gland. Discussion To our knowledge, the course of illness described in this patient represents the longest period of survival ever recorded after severe, pathologically documented primary traumatic injury to the brainstem. Although there are a few reports in the literature of relatively long sur-
Figure 4. Photomicrograph of the caudal midbrain. Note the pallor of staining of those portions of the cerebralpeduncles occupied by descending corticospinal fibers (arrows) (Kliiver-Barrera: x 4.7L
528
Surg Neurol 1985;23:525-8
vival after autopsy-confirmed primary brainstem injury of comparable severity [10,18,19], these cases differ from the one presented here in two major respects: (a) clinically, there was marked impairment of intellectual function or level of consciousness, and (b) pathologically, there was evidence of widespread brain damage. The location and extent of the lesion within the basis pontis account for the patient's transitory "locked-in" state and for all of the residual neurologic deficits. Preservation of intellect and the relative sparing of function in the left upper extremity undoubtedly contributed to his unusually long survival. That the brainstem lesion was of primary rather than of secondary nature is indicated by its ventral and caudal location within the pons, by the absence of any longstanding structural abnormalities above the tentorium, and by the absence of any old foci of pressure necrosis within the cingulate or parahippocampal gyri [ 1,6,17,18 ]. In accordance with the suggestion made by others [ 1,17,18], we believe that primary traumatic lesions within the basis pontis, such as the one we have described here, are most probably the result of shearing of axons at the moment of impact. We think it unlikely, on the basis of its pathologic appearance, that a hematoma had developed at the site of injury. Traumatic vascular occlusion also is not likely to have been responsible, in view of the histopathologically normal appearance of the basilar artery. The presence of retrograde degeneration within the corticospinal tracts confirms the observations of others [5,7,9,11] in both human and animal material. Whether there is a loss of Betz cells or merely a reduction in their volume after transection of the pyramidal tracts, however, is a matter of considerable debate [7,11]. In this instance, examination of many sections of motor cortex suggested a considerable reduction in the concentration of Betz cells on either side, although no attempt at quantitative analysis was made, largely because of the presence of widespread ischemic cell change. Particularly noteworthy is our failure to find evidence of widespread injury (in the form of microglial stars, axonal retraction balls, or ventricular enlargement) at other sites within the central nervous system. Many investigators have emphasized the great rarity with which the brainstem is affected in the absence of cerebral hemispheric injury after blunt trauma [2-4, 13,14,16,19]; indeed, the view has been expressed that, except for the pontomedullary rent that may develop after a hyperextension injury, primary traumatic brainstem lesions do not occur in isolation [2-4,13]. The findings in the case that forms the basis of this report, however, clearly establish that severe primary brainstem injury may occur in the absence of diffuse cerebral damage, and that the
Kim et al
possibility of such an occurrence, though rare, must be borne in mind when dealing with the head-injured patient. This study was supported in part by Grant ES 02928 from the National Institute of Environmental Health Sciences.
References 1. Adams H, Graham DI. The pathology of blunt head injuries. In: Critchley M, O'Leary JL, Jennett B, eds. Scientific foundations of neurology. Philadelphia: PA Davis, 1972:478-91. 2. Adams JH. The neuropathology of head injuries. In: Vinken PJ, Bruyn GW, Braakman R, eds. Handbook of clinical neurology, Vol 23. Amsterdam: North-Holland, 1975:35-65. 3. Adams JH, Gennarelli TA, Graham DI. Brain damage in nonmissile head injury: observations in man and subhuman primates. In: Smith WT, Cavanagh JB, eds. Recent advances in neuropathology, No. 2. Edinburgh: Churchill Livingstone, 1982:165-90. 4. Adams JH, Mitchell DE, Graham DI, Doyle D. Diffuse brain damage of immediate impact type: its relationship to 'primary brain-stem damage' in head injury. Brain 1977;100:489-502. 5. Bronson R, Gilles FH, Hall J, Hedley-White ET. Long-term posttraumatic retrograde corticospinal degeneration in man. Hum Pathol 1978;9:602-7. 6. Crompton MR. Brainstem lesions due to closed head injury. Lancet 1971:669-73. 7. Feringa ER, Vahlsing HL, Smith BE. Retrograde transport in corticospinal neurons after spinal cord transection. Neurology 1983;33:478-82. 8. Harding B, Erdohazi M. Traumatic transection of the brainstem. J Neurol Neurosurg Psychiatry 1981;444:1156-8. 9. Holmes G, May WP. On the exact origin of the pyramidal tracts in man and other animals. Brain 1909;32:1-43. 10. Huhn B, Jakob H. Traumatische Hirnstamml~isionen mit vielj~ihriger Uberlebensdauer. Beitrag zur Pathologie der Substantia nigra und der oralen Briickenhaube. Nervenarzt 1970;41:326-34. 11. Kalil K, Schneider GE. Retrograde cortical and axonal changes following lesions of the pyramidal tract. Brain Res 1975;89:15-27. 12. Lindenberg R, Freytag E. Brainstem lesions characteristic of traumatic hyperextension of the head. Arch Pathol 1970;90:509- l 5. 13. Mitchell DE, Adams JH. Primary focal impact damage to the brainstem in blunt head injuries: does it exist? Lancet 1973;ii:215-8. 14. Ommaya AK, Gennarelli TA. Cerebral concussion and traumatic unconsciousness: correlation of experimental and clinical observations on blunt head injuries. Brain 1974;97:633-54. 15. Pilz P, Strohecker J, Brobovschek M. Survival after traumatic ponto-medullary tear. J Neurol Neurosurg Psychiatry 1982; 45:422-7. 16. Rosenblum WI, Greenberg RP, SeeligJM, Becker DP. Midbrain lesions: frequent and significant prognostic feature in closed head injury. Neurosurgery 1981;9:613-20. 17. Strich SJ. Shearing of nerve fibres as a cause of brain damage due to head injury: a pathological study of twenty cases. Lancet 1961;ii:443-8. 18. Tomlinson BE. Brain-stem lesions after head injury. J Clin Pathol 1970;23(Suppl 4): 154-65. 19. Zolt~in L. Clinico-pathological changes in cases of traumatic brain stem lesions with long survival. In: De Vet AC, ed. Proceedings of the Third International Congress of Neurological Surgery, Copenhagen, 1965. International Congress Series No 110. Amsterdam: Excerpta Medica, 1966:151-6.