Bilateral traumatic abducens palsy. A mechanism of injury suggested by the study of associated cervical spine fractures

Unveiling the vulnerability of the human abducens nerve: insights from comparative cranial base anatomy in mammals and primates

The topographic anatomy of the abducens nerve has been the subject of research for more than 150 years. Although its vulnerability was initially attributed to its length, this hypothesis has largely lost prominence. Instead, attention has shifted toward its intricate anatomical relations along the cranial base. Contrary to the extensive anatomical and neurosurgical literature on abducens nerve anatomy in humans, its complex anatomy in other species has received less emphasis. The main question addressed here is why the human abducens nerve is predisposed to injury. Specifically, we aim to perform a comparative analysis of the basicranial pathway of the abducens nerve in mammals and primates. Our hypothesis links its vulnerability to cranial base flexion, particularly around the sphenooccipital synchondrosis. We examined the abducens nerve pathway in various mammals, including primates, humans (N = 40; 60% males; 40% females), and human fetuses (N = 5; 60% males; 40% females). The findings are presented at both the macroscopic and histological levels. To associate our findings with basicranial flexion, we measured the cranial base angles in the species included in this study and compared them to data in the available literature. Our findings show that the primitive state of the abducens nerve pathway follows a nearly flat (unflexed) cranial base from the pontomedullary sulcus to the superior orbital fissure. Only the gulfar segment, where the nerve passes through Dorello's canal, demonstrates some degree of variation. We present evidence indicating that the derived state of the abducens pathway, which is most pronounced in humans from an early stage of development, is characterized by following the significantly more flexed basicranium. Overall, the present study elucidates the evolutionary basis for the vulnerability of the abducens nerve, especially within its gulfar and cavernous segments, which are situated at the main synchondroses between the anterior, middle, and posterior cranial fossae-a unique anatomical relation exclusive to the abducens nerve. The principal differences between the pathways of this nerve and those of other cranial nerves are discussed. The findings suggest that the highly flexed human cranial base plays a pivotal role in the intricate anatomical relations and resulting vulnerability of the abducens nerve.

Effect of clival bone growth on the localization of the abducens nerve at the petroclival region: a postmortem anatomical study

PURPOSE

To investigate the effect of the clival bone pattern on the abducens nerve (AN) localization in the petroclival region between the Pediatric and Adult Groups.

METHODS

This study used 12 pediatric and 17 adult heads obtained from the autopsy. The length and width of the clivus and the length of the petrosphenoidal ligaments (PSLs) were measured. The ratio of the length and width of the clivus was accepted as the clival index (CI). The localization of the AN at the petroclival region below the PSL, classified as lateral and medial, were recorded.

RESULTS

The average length of the clivus was 26.92 ± 2.88 mm in the Pediatric Group, and 40.66 ± 4.17 mm in the Adult Group (p < 0.001). The average width of the clivus was 22.35 ± 2.88 mm in the Pediatric Group, and 29.96 ± 3.86 mm in the Adult Group (p < 0.001). The average value of the CI was 1.20 in the Pediatric Group and 1.36 in the Adult Group (p = 0.003). The length of the PSL was 7.0 ± 1.47 mm in the Pediatric Group and 11.05 ± 2.95 mm in the Adult Group (p < 0.001). The nerve was located below the medial side of the PSL in the Pediatric Group and below the lateral side in the Adult Group (p = 0.002).

CONCLUSIONS

The petrous apex localization of the AN in adults compared with pediatric subjects could be related to the increased growth in the length of the clivus than its width.

Bilateral traumatic abducens nerve avulsion: A case series and literature review

Although abducens nerve palsy is an established sequela of head trauma - given the prolonged intracranial course of the nerve - bilateral injury is rare. Here, we present two cases of bilateral traumatic abducens nerve avulsion, in the absence of regional fractures, one of which presented two months following the initial trauma. Additionally, we review the current literature on bilateral abducens nerve palsy secondary to trauma, discussing the anatomy of the nerve's course and potential mechanisms of injury.

Anatomic variation of the abducens nerve in a single cadaver dissection: the "petrobasilar canal"

Anatomic variations of the petrosphenoid ligament, Dorello's canal and the course of the abducens nerve have been extensively described over the past years. In the present report of a single cadaver dissection, we describe an unusual course of the abducens nerve at the level of the petrous bone. The right abducens nerve did not enter Dorello's canal, but ran below the petrous bone through a narrow canal in the petrobasilar suture, which we called the "petrobasilar canal". No anatomic variations of the left abducens nerve were noted.

Bilateral abducens nerve palsy following ligamentous C1-C2 distraction

PURPOSE

Posttraumatic abducens nerve palsy is well documented following head injury, but only few case reports exist on sixth nerve palsy after cervical spine trauma. Bilateral abducens palsy following vertical C1-C2 ligamentous distraction has not been described yet.

METHODS

We report two patients who sustained motor vehicle accident-related C1-C2 distraction injury and were diagnosed with posttraumatic bilateral abducens nerve palsy.

RESULTS

Patients underwent surgical stabilization of the upper cervical spine and demonstrated a remarkable recovery of the sixth nerve deficit up to 1 year after injury.

CONCLUSION

We hypothesize that ligamentous C1-C2 distraction leads to caudal displacement of the brainstem in relation to the cranial base causing traction injury to the abducens nerve at its entry into Dorello's canal in the cavernous sinus.

Trauma of the upper cervical spine: focus on vertical atlantoaxial dislocation

PURPOSE

Traumatic ligament injuries of the craniovertebral junction, either isolated or associated with bone avulsion or fracture, often lead to death. These injuries are rare and underrated but are increasingly seen in emergency departments due to the improvement in initial on-scene management of accidents. Vertical atlantoaxial dislocation (AAD) is a specific lesion that was barely reported. Based on our experience, our goal was to systematically investigate the prevalence and prognosis of traumatic vertical AAD and discuss its management.

METHODS

All cervical CT scans performed at our institution between 2006 and 2010 for cervical trauma in adults were retrospectively reviewed. Based on the measurement of lateral mass index (LMI), defined as the gap between C1 and C2 articular facets, we identified three cases of traumatic vertical AAD in 300 CT scans. Their medical records were investigated.

RESULTS

The incidence of vertical AAD was 1% in the exposed population. One case was an isolated vertical AAD and two were associated with a type II odontoid fracture. We report the first case in the literature of unilateral vertical AAD. Two patients died rapidly; the survivor was treated with occipitocervical fixation. Specific maneuvers were used for immobilization and reduction.

CONCLUSIONS

This study found a not insignificant incidence of vertical AAD and a high lethality rate. LMI appears to be a relevant radiological criterion for this diagnosis, for which traction is contraindicated. Associated neurological or vascular damage should be suspected and investigated. In our experience, spinal surgical fixation is required because of major instability.

The Dorello canal: historical development, controversies in microsurgical anatomy, and clinical implications

Interest in studying the anatomy of the abducent nerve arose from early clinical experience with abducent palsy seen in middle ear infection. Primo Dorello, an Italian anatomist working in Rome in the early 1900s, studied the anatomy of the petroclival region to formulate his own explanation of this pathological entity. His work led to his being credited with the discovery of the canal that bears his name, although this structure had been described 50 years previously by Wenzel Leopold Gruber. Renewed interest in the anatomy of this region arose due to advances in surgical approaches to tumors of the petroclival region and the need to explain the abducent palsies seen in trauma, intracranial hypotension, and aneurysms. The advent of the surgical microscope has allowed more detailed anatomical studies, and numerous articles have been published in the last 2 decades. The current article highlights the historical development of the study of the Dorello canal. A review of the anatomical studies of this structure is provided, followed by a brief overview of clinical considerations.

Delayed post-traumatic bilateral abducens nerve palsy with complete recovery

Isolated bilateral abducens (sixth) nerve palsy is rare in the setting of trauma. To date, most cases have been reported in patients who sustain cranial fractures or have other acute intracranial pathologies, including acute hemorrhage. We describe the case of a 41-year-old man who presented with bilateral abducens nerve palsy in the setting of acute head trauma without evidence of cranial fractures or other acute intracranial pathology. Six months after the initial injury, he regained bilateral function of his abducens nerves with intact extraocular muscle movements. Full recovery is the natural history in the majority of traumatic abducens nerve palsies, and this is an important consideration when counseling patients with such injuries.

Orbitoethmoidal impacted injury by kitchen knife causing abducens nerve palsy

INTRODUCTION

Impacted knife injuries in the maxillofacial region are rare and infrequently reported. In cases of injury involving orbit or eye, these reports are even rarer.

DISCUSSION

Damage to the orbital contents may result in a rupture of the globe, extraocular muscle injury, lacrimal gland damage, and others. Orbital foreign bodies are not only difficult to detect, and clinical features vary according to its size, characteristics, shape, penetrating method, and site. In this report, a case of abducens nerve palsy after orbitoethmoidal knife injury is presented.

Clival epidural hematoma in traumatic sixth cranial nerve palsies combined with cervical injuries

Eight patients sustained a combination of clival epidural hematoma, traumatic sixth cranial nerve palsy (6 NP), and occipitocervical injury. This combination of features has been sparsely described. Whether the hematoma, which represents tectorial membrane injury, is merely a marker for 6 NP and occipitocervical injury or is causative is unresolved, but this imaging finding should alert examiners who note traumatic 6 NP to the need for detailed cervical imaging, as surgical stabilization of this region may be critical to prevent future spinal cord dysfunction.

Isolated Bilateral Abducens Nerve Palsy Associated with Traumatic Prepontine Hematoma

We describe a 15-year-old boy who developed isolated bilateral abducens nerve palsies immediately following a motor vehicle accident and who was found to have a pre-pontine extra-axial hematoma. We review the literature on isolated bilateral traumatic abducens palsies and discuss the alternate mechanisms for this injury.

Clinical analysis of seven patients of crushing head injury

BACKGROUND

Crushing head injuries (CHI) are caused by static loading. This static force slowly deforms a cranium and damages some intracranial components. Severe CHI is usually fetal but substantial brain damage may not be recognized in some patients. In this article, we report seven patients who sustained CHI and analyzed clinical and radiological findings.

METHODS

In seven patients who sustained CHI, the following factors were analyzed: epidemiological features, neurological findings, and neuroradiological findings.

RESULTS

The present series included three males and four females. Mean age was 5.9 years. Six patients had the heads run over by automobiles. One patient had the head crushed by press machine. Epistaxis in six patients and otorrhagia in five patients was recognized. Mean Glasgow coma scale at admission was 8.1. Multiple linear fractures were recognized in four patients and skull base fractures in six patients. Pneumocephalus in five patients and cerebrospinal fluid leakage in seven patients was recognized. One patient underwent evacuation of ASDH and dural plasty. Four patients died and three survived and had only cranial nerve palsies, which recovered completely.

CONCLUSION

This injury actually has seldom been countered in daily practice and clinical manifestation and neuroimaging have characteristic features. The prognosis of CHI may be polarized to fatal or excellent, and depends on whether the cranium and brain itself can tolerate the applied force.

Third, fourth, and sixth cranial nerve palsies following closed head injury

BACKGROUND

The relationship between the circumstances and severity of closed head injury (CHI) and the clinical and imaging features of cranial nerve 3, 4, and 6 palsies has not been rigorously addressed in a large study.

METHODS

Retrospective chart review of 210 consecutive patients with CHI examined at a single tertiary care center from 1987 to 2002. Patients were located by searching the ophthalmology inpatient consultation and neuro-ophthalmology outpatient databases and hospital emergency room billing codes for a diagnosis of traumatic 3, 4, or 6 cranial nerve palsy (Cranial Nerve Injury Group) and a diagnosis of CHI without traumatic 3, 4, or 6 nerve palsy (Control Group). The Cranial Nerve Injury Group was then subdivided into two groups: those with injuries to an individual cranial nerve and those with multiple (including bilateral) cranial nerve injuries. Comparisons between groups were based on age, gender, type of accident, Glasgow Coma Scale (GCS), documented loss of consciousness (LOC), type of ocular injury, presence of systemic injury, need for rehabilitation, physical therapy and cognitive scores, and imaging features.

RESULTS

The Cranial Nerve Injury Group had a significantly higher severity of head injury, more CT abnormalities, and worse short-term neurologic outcomes as compared with the Control Group. These trends were also found when each cranial nerve injury subgroup was compared with the Control Group. Those with cranial nerve 3 palsy had the most severe head injury; those with cranial nerve 4 palsy had an intermediate level of head injury; and those with cranial nerve 6 palsy had the lowest level of head injury. There were no consistent associations between the location of the imaging abnormalities and which cranial nerve was damaged.

CONCLUSIONS

CHI with palsy of an ocular motor nerve was more severe than CHI without ocular motor nerve palsy, as measured by the GCS, intracranial and skull imaging abnormalities, and a greater frequency of inpatient rehabilitation. Palsy of cranial nerve 3 was associated with relatively more severe CHI than was palsy of cranial nerves 4 or 6. The location of the imaging abnormalities did not correlate with a particular cranial nerve injury.

Abducens Nerve Palsy in a Patient With a Parasagittal Meningioma

A 67-year-old female presented with isolated unilateral abducens nerve palsy progressing in 10 days. There were no signs of elevated intracranial pressure. Magnetic resonance imaging revealed a right parasagittal meningioma. The tumor was grossly totally removed and the patient's nerve palsy gradually improved within 3 weeks. The mechanism of the isolated abducens nerve palsy in this case is attributed to compression of the abducens nerve by entrapment of the cerebrospinal fluid just before entering Dorello's canal under the petrolingual ligament. Linear forces in the midsagittal plane due to the mass effect of the tumor may have temporarily increased the local cerebrospinal fluid pressure and caused 'pseudoentrapment' of the abducens nerve.

Ocular and visual complications of head injury

PURPOSE

To evaluate the pattern of ocular and visual complications of head injury.

METHOD

A prospective study of 225 head-injured patients managed at the University of Ilorin Teaching Hospital, Ilorin, Nigeria. For the purpose of extracting visual complications, a Neurosurgeon and an Ophthalmologist examined each patient and appropriate investigations were carried out. Patients with ocular morbidity were analysed for age, sex, cause of injury, admission Glasgow coma score, and associated injuries in addition to findings at ophthalmic and neurosurgical evaluations.

RESULTS

Two major types of ocular and visual complications were observed in 57 (25.3%) of 225 head-injured patients studied. Soft-tissue injury to the globe and adnexae included periorbital ecchymosis, subconjuctival haemorrhage, lid laceration, or rarely globe rupture in 29 patients. Neuro-ophthalmic ocular cranial nerve palsies occurred in 28 patients, while orbital fracture was encountered in two patients. Ocular injuries were multiple in 60% of cases. The patients, comprising 37 male and 20 female subjects, were aged 9 months to 57 years (mean=28 years). Traffic accident was the leading cause of head injuries (84.2%), while fall from height (7%), assault (7%), and gunshot (1.8%) were miscellaneous causes.

CONCLUSION

Injury to the globe and adnexae and ocular cranial nerve palsies constitute the most common oculovisual complications following head injury in our centre.

Bitemporal head crush injuries: clinical and radiological features of a distinctive type of head injury

OBJECT

Most craniocerebral injuries are caused by mechanisms of acceleration and/or deceleration. Traumatic injuries following progressive compression to the head are certainly unusual. The authors reviewed clinical and radiological features in a series of patients who had sustained a special type of cranial crush injury produced by the bilateral application of rather static forces to the temporal region. Their aim was to define the characteristic clinical features in this group of patients and to assess the mechanisms involved in the production of the cranial injuries and those of the associated cerebral and endocrine lesions found in this peculiar type of head injury.

METHODS

Clinical records of 11 patients were analyzed with regard to the state of consciousness, cranial nerve involvement, findings on neuroimaging studies, endocrine symptoms, and outcome. Furthermore, an experimental model of bitemporal crush injury was developed by compressing a dried skull with a carpenter's vice. Seven of the 11 patients were 16 years old or younger. All patients presented with a characteristic clinical picture consisting of no loss of consciousness (six patients), epistaxis (nine patients), otorrhagia (11 patients), peripheral paralysis of the sixth and/or seventh cranial nerves (10 patients), hearing loss (five patients), skull base fractures (11 patients), pneumocephalus (11 patients), and diabetes insipidus (seven patients). Ten patients survived the injury and most recovered neurological function.

CONCLUSIONS

Static forces applied to the head in a transverse axis produce fractures in the skull base that cross the midline structures without producing significant cerebral damage. Stretching of cranial nerves at the skull base explains the nearly universal finding of paralysis of these structures, whereas an increase in the vertical diameter of the skull accounts for the occurrence of diabetes insipidus in the presence of an intact function of the anterior pituitary lobe. The association of clinical, endocrine, and neuroimaging findings encountered in this peculiar type of head injury supports the idea that this subset of injured patients has a distinctive clinical condition, namely the syndrome of bitemporal crush injury to the head.

The mechanism of injury of the abducens nerve in severe head trauma: a postmortem study

The aim of this study is to investigate the mechanism of injury of abducens nerve at petroclival region in severe head trauma. Twenty specimens provided from 10 autopsied cases due to severe head trauma were investigated macroscopically and histopathogically. The slices of the abducens nerve taken consecutively along its course at petroclival region were stained with Hematoxylline-Eosin and evaluated under light microscope. In addition, coexisting cervical injuries in these cases were assessed macroscopically. Edema and perineural hemorrhagia of abducens nerve were identified in all cases. Nerve injury was found more exaggerated at the sites of dural entry point and petrous apex than any other parts of the abducens nerve. Furthermore, microscopically, also remarkable perineural hemorrhage of the abducens nerve was observed at the site of its anastomoses with the sympathetic plexus on the lateral wall of the internal carotid artery (ICA). Abducens nerve is injured at the sites of dural entry point, petrous apex and lateral wall of the ICA, directly proportional with the severity of the trauma. This finding is also significant in verification of the severe head trauma.

Isolated abducens nerve paresis associated with incomplete Horner's syndrome caused by petrous apex fracture--case report and anatomical study

A 17-year-old male presented with a wound on the right temporal region, oozing hemorrhagic necrotic brain tissue and cerebrospinal fluid, following a fall. Computed tomography showed temporoparietal and petrous apex fractures on the right. Neurological examination revealed abducens nerve paresis, ptosis, and myosis on the right side. The patient was treated surgically for the removal of the free bony fragments at the fracture site and to close the dural tear. The abducens nerve paresis, ptosis, and myosis persisted at the 3rd monthly postoperative follow-up examination. The anatomy of the abducens nerve at the petroclival region was studied in four cadaveric heads. Two silicone-injected heads were used for microsurgical dissections and two for histological sections. The abducens nerve has three different angulations in the petroclival region, located at the dural entrance porus, the petrous apex, and the lateral wall of the cavernous segment of the internal carotid artery. The abducens nerve had fine anastomoses with the trigeminal nerve and the periarterial sympathetic plexus. There were fibrous connections extending inside the venous space of the petroclival area. The abducens nerve seems to be vulnerable to damage in the petroclival region, either directly by trauma to its dural porus and petrous apex or indirectly by stretching of the nerve through the nervous and/or fibrous connections. Concurrent functional loss of the abducens nerve and the periarterial sympathetic plexus clinically manifested as incomplete Horner's syndrome in our patient.

Atlanto-occipital dislocation: a report of three patients and a review

Traumatic atlanto-occipital dislocation is usually instantaneously fatal when it occurs. Survival is possible with minimal remaining neurologic deficits if diagnosed quickly and treated appropriately. The authors present three reports of patients who survived the incident, and they review the anatomy of the atlanto-occipital joint, clinical presentation, diagnosis, and treatment of this traumatic injury.

Temporal bone fractures

High-resolution technique is essential to the evolution of temporal bone fractures. Axial and coronal scan planes are optimal but may not be possible in acutely traumatized patients. A knowledge of normal temporal bone anatomy is important and can be obtained from standard texts, so it will not be considered in detail in this article. Classically, petrous temporal bone fractures have been classified as longitudinal, transverse, or mixed. Recent publications have emphasized the importance of describing fractures in terms of planes rather than lines. According to this concept, most temporal bone fractures are actually oblique, and true longitudinal fractures are rare. Petrous temporal bone fractures may be associated with cranial nerve or vascular injuries when the fracture extends to the skull base. This is particularly true of the oblique fracture, which characteristically extends anteromedially to the skull base through weak places in that area, thus avoiding the compact bone of the otic capsule surrounding the labyrinth. The most common associated injury is to the facial nerve in its geniculate or proximal tympanic segment. Transverse fractures frequently involve the labyrinth. A careful search for various types of ossicular dislocation should be performed in association with temporal bone fractures, because this may result in conductive hearing loss. The site of cerebrospinal fluid otorhinorrhea resulting from temporal bone fractures can usually be defined on plain high-resolution temporal bone images, but intrathecal contrast may be helpful. Temporal bone fractures caused by gunshot wounds are frequently complex and may be limited by metallic streak artifacts. Pediatric patients have different proportions of facial nerve injury and types of hearing loss as compared with adults.

Bilateral traumatic abducens nerve paralysis with cervical spine flexion injury

Bilateral traumatic abducens nerve palsy is a rare condition. We report a case associated with cervical spine flexion injury. This may be the first such case report, as no similar case was found in our review of the literature. The mechanisms of injury in this case are relevant to theories that explain hyperextension injuries.

Dorello's canal: a microanatomical study

The microsurgical anatomy of Dorello's canal has been studied in 20 specimens obtained from 10 cadaver heads fixed in formalin. The bow-shaped canal through which courses the abducens nerve before reaching the cavernous sinus is located inside a venous confluence which occupies the space between the dural leaves of the petroclival area. The petrosphenoidal ligament (Gruber's ligament), which forms the posteromedial wall of the canal, appears as a fibrous trabecula surrounded by venous blood. Canal measurements were performed and its anatomical relationship with the sixth cranial nerve is described. Angulations of variable degrees were observed in the course of the nerve inside and outside the canal. The influence of this relatively tortuous course of the abducens nerve upon its vulnerability in some pathological conditions is discussed.

Ocular complications of head injury in children

Ocular complications occurred in 28% of children with head injury. Neuro-ophthalmological lesions made up one-third of these complications, mostly involved the optic nerve, and were associated with other focal neurological signs more frequently than non-neural ocular complications. Lesions of the posterior visual pathways were rare but tended to be permanent.

Ocular motor abnormalities from head trauma

Head injuries cause the hospitalization of 200-300 persons per 100,000 population per year. Ophthalmologists provide diagnostic and therapeutic care to those trauma victims with damage to the globe, optic nerve, orbit, and ocular motor system. Eye movements can be affected by damage at any level of the central nervous system or peripheral motor unit. Comprehensive ocular motor assessment of the trauma patient can substantially contribute to the understanding of the patient's injury, recovery, and rehabilitation. This review examines all aspects of head and face trauma that can lead to ocular motility disturbances.

Bilateral traumatic third nerve palsy

Bilateral palsy of the third cranial nerve in a head-injured patient is described. Delayed computed tomography scanning demonstrated a midline necrotic lesion within the mesencephalon ventral to the aqueduct. The lesion, possibly the sequela of a focal contusion, involved both third nerve nuclear complexes and caused paralysis of their voluntary as well as autonomic functions. Gaze mechanisms and long tracts appeared to be less heavily damaged. The literature dealing with third nerve palsy, particularly bilateral cases, from traumatic and other origins is briefly reviewed.

Multiple cranial nerve palsies due to a hyperextension injury to the cervical spine. Case report

The case of a patient with multiple bilateral cranial nerve palsies and spinal cord sparing secondary to a stable hyperextension injury to C-1 is presented.

Survival after traumatic ponto-medullary tear

Two children (aged 10 and 12 years) were admitted unconscious to the neurosurgical department after traffic accidents. Both developed a 6th nerve paralysis on the next day. One patient was able to communicate from the 2nd day and died on the 8th day in an anuric state without major neurological deficit. The second patient remained deeply comatose, tetraplegic, and required intermittent artificial respiration: She died of pneumonia on the 26th day. Neuropathological examination revealed a ponto-medullary rent in each case: additionally there was avulsion of small arteries over the pyramids, haemorrhage and small focal infarcts in the distribution of perforating arteries in the medulla and pons, and abundant retraction balls in longitudinal fibre tracts of the brain stem. The cases show for the first time that traumatic ponto-medullary tears are not always rapidly fatal, and demonstrate that primary focal brain stem trauma may occur in the absence of diffuse trauma of the white substance.

Recurrent, isolated, post-febrile abducens nerve palsy

A case presenting with three episodes of recurrent benign abducens palsy is reported. The patient experienced her first episode at age of 3 years, her second when she was 13 years old, and the last at the age of 25 during pregnancy. Full recovery was attained within approximately three months after each episode.

Bilateral trigeminal and abducens neuropathies following low-velocity, crushing head injury. Case report

✓ A case is presented of bilateral injury to the trigeminal and abducens nerves following closed head trauma in which the patient survived crushing of the head by a heavy, large-diameter pipe. Bilateral trigeminal and unilateral abducens neuropathies persisted for more than 1 year. These unusual findings are discussed in regard to localization and possible mechanisms of injury. The effects of this type of low-velocity, crushing head injury are compared and contrasted with those of acceleration-deceleration head injuries.

Traumatic atlantooccipital dislocation. Case report

A case of traumatic atlantooccipital dislocation is presented and the literature reviewed. This type of traumatic dislocation is probably produced by violent hyperextension of the upper cervical spine. Cranial nerve injuries and spinal cord injuries are common. Early fusion is recommended.

Lateral rectus muscle paralysis associated with closed-head trauma

We examined 21 patients with closed-head trauma and resulting paralysis of the lateral rectus muscle. Clinical findings included laterally directed gaze palsy, some unconsciousness, and pseudo-duane's phenomenon suggesting a supranuclear lesion at the level of the upper pontine tegmentum, and pontine paramedial reticular formation. The surgical procedure of choice was a "midline operation," that is, the appropriate number of millimeters of recession and resection to achieve 0 to 5 degrees of exotropia in the primary position of gaze. Frequently, the medial rectus muscle must be recessed 10 nm or more and the lateral rectus muscle resected 10 nm or more to achieve this result. None of the 21 patients had diplopia after the midline procedure.