A posttraumatic pontomedullary rent with good outcome.

Posttraumatic pontomedullary rents have been described mainly as postmortem histopathological findings in patients who died immediately or within the first hours after trauma. To the best of our knowledge, no long-term survivors of this condition have been described, and those surviving initially were always severely impaired. We present the first patient with this condition and with corresponding lesions on imaging who survived longer than 3 months. Moreover, the patient regained almost complete independence 1 year after the trauma. We briefly discuss the proposed mechanisms of this injury. We conclude that this lesion, when incomplete, is not always lethal and can exceptionally have a good clinical outcome. Prevention of respiratory failure is of utmost importance in these patients.

Deafferentation in thalamic and pontine areas in severe traumatic brain injury.

PURPOSE: Severe traumatic brain injury (TBI) is characterized mainly by diffuse axonal injuries (DAI). The cortico-subcortical disconnections induced by such fiber disruption play a central role in consciousness recovery. We hypothesized that these cortico-subcortical deafferentations inferred from diffusion MRI data could differentiate between TBI patients with favorable or unfavorable (death, vegetative state, or minimally conscious state) outcome one year after injury. METHODS: Cortico-subcortical fiber density maps were derived by using probabilistic tractography from diffusion tensor imaging data acquired in 24 severe TBI patients and 9 healthy controls. These maps were compared between patients and controls as well as between patients with favorable (FO) and unfavorable (UFO) 1-year outcome to identify the thalamo-cortical and ponto-thalamo-cortical pathways involved in the maintenance of consciousness. RESULTS: Thalamo-cortical and ponto-thalamo-cortical fiber density was significantly lower in TBI patients than in healthy controls. Comparing FO and UFO TBI patients showed thalamo-cortical deafferentation associated with unfavorable outcome for projections from ventral posterior and intermediate thalamic nuclei to the associative frontal, sensorimotor and associative temporal cortices. Specific ponto-thalamic deafferentation in projections from the upper dorsal pons (including the reticular formation) was also associated with unfavorable outcome. CONCLUSION: Fiber density of cortico-subcortical pathways as measured from diffusion MRI tractography is a relevant candidate biomarker for early prediction of one-year favorable outcome in severe TBI.

Spinal and pontine relay pathways mediating respiratory rhythm entrainment by limb proprioceptive inputs in the neonatal rat.

The coordination of locomotion and respiration is widespread among mammals, although the underlying neural mechanisms are still only partially understood. It was previously found in neonatal rat that cyclic electrical stimulation of spinal cervical and lumbar dorsal roots (DRs) can fully entrain (1:1 coupling) spontaneous respiratory activity expressed by the isolated brainstem/spinal cord. Here, we used a variety of preparations to determine the type of spinal sensory inputs responsible for this respiratory rhythm entrainment, and to establish the extent to which limb movement-activated feedback influences the medullary respiratory networks via direct or relayed ascending pathways. During in vivo overground locomotion, respiratory rhythm slowed and became coupled 1:1 with locomotion. In hindlimb-attached semi-isolated preparations, passive flexion-extension movements applied to a single hindlimb led to entrainment of fictive respiratory rhythmicity recorded in phrenic motoneurons, indicating that the recruitment of limb proprioceptive afferents could participate in the locomotor-respiratory coupling. Furthermore, in correspondence with the regionalization of spinal locomotor rhythm-generating circuitry, the stimulation of DRs at different segmental levels in isolated preparations revealed that cervical and lumbosacral proprioceptive inputs are more effective in this entraining influence than thoracic afferent pathways. Finally, blocking spinal synaptic transmission and using a combination of electrophysiology, calcium imaging and specific brainstem lesioning indicated that the ascending entraining signals from the cervical or lumbar limb afferents are transmitted across first-order synapses, probably monosynaptic, in the spinal cord. They are then conveyed to the brainstem respiratory centers via a brainstem pontine relay located in the parabrachial/Kölliker-Fuse nuclear complex.

Pontomedullary lacerations in unhelmeted motorcyclists and bicyclists: a retrospective autopsy study.

Pontomedullary lacerations (PMLs) have often been reported in car occupants and pedestrians, are less frequently described in motorcyclists, and are very rarely described in bicyclists. The aim of this study was to determine the frequency of brainstem PMLs among fatally injured motorcyclists and bicyclists as well as the frequency of concomitant cranial, facial, and cervical spine injuries in such cases. A possible underlying mechanism of PML in fatally injured motorcyclists and bicyclists might thus be established. Of 443 cases of fatally injured motorcyclists and bicyclists, a sample of 381 cases of fatally injured motorcyclists and bicyclists with head injury of Abbreviated Injury Scale score of 3 or greater was formed and further analyzed. This group was composed of 345 men and 36 women. The average age was 48.8 ± 20.8 years (range, 15-99 years). In the analyzed sample group, there were 158 motorcyclists and 223 bicyclists. Partial PMLs were present in 44 cases (12%) within the sample of 381 head injuries, which breaks down to 40 men and 4 women. In our study, the impact area on the head and the specific skull base fracture type were good predictors of either PML occurrence or absence (B = -2.036, Wald = 161.312, P < 0.01, for the whole model). Impact to the chin, with or without a skull base fracture, most often led to this fatal injury due to impact force transmission, either through jawbone or vertebral column. Also, lateral head impact, the most frequent in bicyclists, with subsequent hinge fracture, PML, and frontoposterior hyperextension of the head that is associated with upper spine fracture, could be possible mechanisms of brainstem injury in fatally injured motorcyclists or bicyclists. Our study showed that the jawbone, as well as other facial bones, could act as shock absorbers, and their fracture could diminish energy transfer toward the skull and protect the brain and brainstem from injury.

Pontomedullary lacerations and concomitant head and neck injuries: their underlying mechanism. A prospective autopsy study.

It is a well-documented fact that pontomedullary lacerations (PML) occur as a result of severe craniocervical injury, but their underlying mechanism has yet to be fully clarified. The aim of this prospective study has been to give greater insight into the underlying mechanism of PML through determining the site of blunt head-impact, as well as the presence of concomitant head and neck injuries in cases of brainstem PML. A total of 56 cases with partial PML have been analysed for this study. The case group was composed of 40 men and 16 women, averaging in age 44.2 ± 19.2 years and consisting of 7 motorcyclists, 4 bicyclists, 18 car occupants, 16 pedestrians, and 10 victims of falls from a height, as well as 1 victim of a fall from standing height. The presented study has shown that there are several possible mechanisms of PML. Impact to the chin, with or without a skull base fracture, most often leads to this fatal injury, due to the impact force transmission either through the jawbone or vertebral column; most likely in combination with a fronto-posterior hyperextension of the head. Additionally, lateral head-impacts with subsequent hinge fractures and PML may also be a possible mechanism. The jawbone and other facial bones are able to act as shock absorbers, and their fracture may diminish the energy transfer towards the skull and protect the brain and brainstem from injury. The upper cervical spine can act as damper and energy absorber as well, and may prevent any occurrence of fracture to the base of the skull.

Enhancement of synchronization between hippocampal and amygdala theta waves associated with pontine wave density.

Theta waves in the amygdala are known to be synchronized with theta waves in the hippocampus. Synchronization between amygdala and hippocampal theta waves is considered important for neuronal communication between these regions during the memory-retrieval process. These theta waves are also observed during rapid eye movement (REM) sleep. However, few studies have examined the mechanisms and functions of theta waves during REM sleep. This study examined correlations between the dynamics of hippocampal and amygdala theta waves and pontine (P) waves in the subcoeruleus region, which activates many brain areas including the hippocampus and amygdala, during REM sleep in rats. We confirmed that the frequency of hippocampal theta waves increased in association with P wave density, as shown in our previous study. The frequency of amygdala theta waves also increased with in associated with P wave density. In addition, we confirmed synchronization between hippocampal and amygdala theta waves during REM sleep in terms of the cross-correlation function and found that this synchronization was enhanced in association with increased P wave density. We further studied theta wave synchronization associated with P wave density by lesioning the pontine subcoeruleus region. This lesion not only decreased hippocampal and amygdala theta frequency, but also degraded theta wave synchronization. These results indicate that P waves enhance synchronization between regional theta waves. Because hippocampal and amygdala theta waves and P waves are known to be involved in learning and memory processes, these results may help clarify these functions during REM sleep.

Lateral parabrachial nucleus mediates shortening of expiration and increase of inspiratory drive during hypercapnia.

We have previously shown that unilateral or bilateral lesions of the lateral parabrachial nucleus (LPBN) in anesthetized, vagotomized rats markedly and selectively attenuate the shortening of expiratory duration (T(E)) during hypoxia without appreciably affecting all other hypoxic response components. Here, we report that unilateral LPBN lesion by kainic acid in the same group of animals not only abolished normal T(E)-shortening during central chemoreceptors activation by hyperoxic hypercapnia, but led to paradoxical T(E)-prolongation and corresponding decrease of respiratory frequency. Furthermore, LPBN lesion significantly attenuated the increase in phrenic activity during hyperoxic hypercapnia, without appreciably affecting the corresponding shortening of inspiratory duration (T(I)). These findings provide the first evidence indicating that central chemoafferent inputs are organized in parallel and segregated pathways that separately modulate inspiratory drive, T(I), and T(E) in conjunction with similar parallel and segregated central processing of peripheral chemoafferent inputs reported previously [Young, D.L., Eldridge, F.L., Poon, C.S., 2003. Integration-differentiation and gating of carotid afferent traffic that shapes the respiratory pattern. J. Appl. Physiol. 94, 1213-1229].

Lateral parabrachial nucleus mediates shortening of expiration during hypoxia.

Acute hypoxia elicits complex time-dependent responses including rapid augmentation of inspiratory drive, shortening of inspiratory and expiratory durations (T(I), T(E)), and short-term potentiation and depression. The central pathways mediating these varied effects are largely unknown. Here, we show that the lateral parabrachial nucleus (LPBN) of the dorsolateral pons specifically mediates T(E)-shortening during hypoxia and not other hypoxic response components. Twelve urethane-anesthetized and vagotomized adult Sprague-Dawley rats were exposed to 1-min poikilocapnic hypoxia before and after unilateral kainic acid or bilateral electrolytic lesioning of the LPBN. Bilateral lesions resulted in a significant increase in baseline T(E) under hyperoxia. After unilateral or bilateral lesions, the decrease in T(E) during hypoxia was markedly attenuated without appreciable changes in all other hypoxic response components. These findings add to the mounting evidence that the central processing of peripheral chemoafferent inputs is segregated into parallel integrator and differentiator (low-pass and high-pass filter) pathways that separately modulate inspiratory drive, T(I), T(E) and resultant short-term potentiation and depression.

Removal of a chopstick out of the cavernous sinus, pons, and cerebellar vermis through the superior orbital fissure.

Penetrating non-missile orbito cranial injuries are rare in a civilian pediatric setting. We describe a case of a trans-orbital penetration by a wooden chopstick deep down into the cerebellar vermis detected at neuroradiological examination in a child presenting for head injury. The foreign body was successfully pulled out in one piece surgically.

The discrepant severity of external and internal injuries in a traffic accident: The cushioning effect via a human body against direct impact: Autopsy cases.

Traffic accidents cause unexpectedly severe injuries of internal organs despite tiny injuries observed on the external body. A 51-year-old woman (subject 1) and a 54-year-old man (subject 2) were found dead on a road. Subject 1 had subcutaneous and intramuscular bleeding with décollement on the posterior aspect of her body, including upper cervical spine dislocation. Subject 2 did not exhibit any apparent findings on autopsy that were indicative of a direct injury by a motor vehicle, but had severe internal organ injuries, including the transection at the pontomedullary junction. We surmise that subjects 1 and 2 were walking in line with the vehicle which collided with them from behind, and then the body of subject 1 cushioned the direct impact of the vehicle against subject 2. This report illustrates the need of forensic autopsy for victims with no severe external injuries.

Near-total absence of REM sleep co-occurring with normal cognition: an update of the 1984 paper.

BACKGROUND: REM sleep (REMS) is considered vital for supporting well-being and normal cognition. However, it remains unclear if and how decreases in REMS impair cognitive abilities. Rare case studies of patients with REMS abolishment due to pontine lesions remain sporadic, and formal evaluation of cognitive status is lacking. In 1984, Lavie and colleagues described the case of Y.C. - a man with a pontine lesion and near-total absence of REMS who led a normal life. Here, we set out to re-evaluate this individual's REMS status 30 years after the original report, and formally assess his cognitive abilities. METHODS: Four whole-night polysomnographic sleep recordings were conducted to evaluate sleep architecture. Sleep scoring was performed according to the American Academy of Sleep Medicine (AASM) guidelines. Cranial Computed Tomography (CT) imaging was performed, as well as formal neuropsychological testing to evaluate cognitive functions. RESULTS: Y.C. averaged 4.5% of sleep time in REMS, corresponding to the 0.055 percentile of normal values for his age. Furthermore, residual REMS episodes were short and only occurred towards the end of the night. CT imaging revealed damage and metallic fragments in pons, cerebellum, and thalamus. Neuropsychological evaluation demonstrated average to high-average cognitive skills, normal memory, and motor difficulties including speech and left hand dyspraxia. CONCLUSIONS: To our knowledge, this is the only case where REMS loss resulting from pontine lesion was re-evaluated after many years. We find a near-total absence of REMS with no signs of significant compensation throughout adult life, along with normal cognitive status. The results provide a unique perspective on the ongoing debate regarding the functional role of REMS in supporting cognition.

cerebellar atrophy after moderate-to-severe pediatric traumatic brain injury.

BACKGROUND AND PURPOSE: Although the cerebellum has not attracted the same degree of attention as cortical areas and the hippocampus in traumatic brain injury (TBI) literature, there is limited structural and functional imaging evidence that the cerebellum is also vulnerable to insult. The cerebellum is emerging as part of a frontocerebellar system that, when disrupted, results in significant cognitive and behavioral consequences. We hypothesized that cerebellar volume would be reduced in children following TBI and wished to examine the relation between the cerebellum and known sites of projection, including the prefrontal cortex, thalamus, and pons. MATERIALS AND METHODS: Quantitative MR imaging was used to measure cerebellar white and gray matter and lesion volumes 1-10 years following TBI in 16 children 9-16 years of age and 16 demographically matched typically developing children 9-16 years of age. Cerebellar volumes were also compared with volumetric data from other brain regions to which the cerebellum projects. RESULTS: A significant group difference was found in cerebellar white and gray matter volume, with children in the TBI group consistently exhibiting smaller volumes. Repeating the analysis after excluding children with focal cerebellar lesions revealed that significant group differences still remained for cerebellar white matter (WM). We also found a relation between the cerebellum and projection areas, including the dorsolateral prefrontal cortex, thalamus, and pons in 1 or both groups. CONCLUSION: Our finding of reduced cerebellar WM volume in children with TBI is consistent with evidence from experimental studies suggesting that the cerebellum and its related projection areas are highly vulnerable to fiber degeneration following traumatic insult.

Injury of the cortico-ponto-cerebellar tract in a patient with mild traumatic brain injury: A case report.

RATIONALE: We report on a patient with injury of the cortico-ponto-cerebellar tract (CPCT) following mild traumatic brain injury (TBI), diagnosed by diffusion tensor tractography (DTT). PATIENT CONCERNS: A 53-year-old female patient was injured in a car crash. While under treatment at a local medical center for headache, mild motor weakness, and cognitive impairment that developed following the car crash, she fell, hitting her head on the ground, about six weeks after the car crash. DIAGNOSES: Approximately three months after the car crash, she began to show tremor on both hands and mild truncal ataxia. Twenty months after the car crash, when she underwent neurological evaluation at the rehabilitation department of a university hospital, she presented with mild resting and intentional tremor on both hands, and mild truncal ataxia. INTERVENTIONS: N/A. OUTCOMES: On 20-month DTT, the left CPCT showed tearing at the level of the subcortical white matter and pons, and discontinuation at the cerebellar portion. However, the integrity of the DRTT was well-preserved in both hemispheres. LESSONS: Using DTT, injury of the CPCT was demonstrated in a patient with ataxia and tremor following mild TBI.

Role of A5 noradrenergic neurons in the chemoreflex control of respiratory and sympathetic activities in unanesthetized conditions.

The A5 area at the ventrolateral pons contains noradrenergic neurons connected with other medullary areas involved in the cardiorespiratory control. Its contribution to the cardiorespiratory regulation was previously evidenced in anesthetized conditions. In the present study, we investigated the involvement of the A5 noradrenergic neurons to the basal and chemoreflex control of the sympathetic and respiratory activities in unanesthetized conditions. A5 noradrenergic neurons were lesioned using microinjections of anti-dopamine ß-hydroxylase saporin (anti-DßH-SAP). After 7-8days, we evaluated the arterial pressure levels, heart rate and minute ventilation in freely moving adult rats (280-350g) as well as recorded from thoracic sympathetic (tSN) and phrenic nerves (PN) using the arterially perfused in situ preparation of juvenile rats (80-90g). Baseline cardiovascular, sympathetic and respiratory parameters were similar between control (n=7-8) and A5-lesioned rats (n=5-6) in both experimental preparations. In adult rats, lesions of A5 noradrenergic neurons did not modify the reflex cardiorespiratory adjustments to hypoxia (7% O2) and hypercapnia (7% CO2). In the in situ preparations, the sympatho-excitation, but not the PN reflex response, elicited by either the stimulation of peripheral chemoreceptors (ΔtSN: 110±12% vs 58±8%, P<0.01) or hypercapnia (ΔtSN: 9.5±1.4% vs 3.9±1.7%, P<0.05) was attenuated in A5-lesioned rats compared to controls. Our data demonstrated that A5 noradrenergic neurons are part of the circuitry recruited for the processing of sympathetic response to hypoxia and hypercapnia in unanesthetized conditions.

Predictors of Surgical Results in Patients with Primary Pontine Hemorrhage.

AIM: Prediction of outcome for surgical patients with primary pontine hemorrhage (PPH) is seldom reported although many predictors from clinical and radiological features have been identified in conservative patients. The purpose of this study was to assess the prognostic factors affecting the 30-day mortality and 3-month functional outcome in surgical patients after PPH. MATERIAL AND METHODS: Forty-five patients with large PPH ( > 5 ml) and Glasgow Coma Scale (GCS) score < 8 were treated surgically at West China Hospital. The demographic, clinical, imaging and follow-up data were collected retrospectively. Factors affecting the mortality and functional outcome were statistically analyzed. RESULTS: Fourteen patients (31.1%) died within 30 days and 7 patients (15.6%) gained a favorable functional recovery within 3 months. A multivariate analysis showed that the hematoma volume, GCS score on admission, age, and type of hemorrhage were all significantly related to the 30-day mortality, while the hematoma volume, GCS score on admission, rostrocaudal extension were associated with the 3-month functional outcome. The presence of hydrocephalus was not found responsible for the surgical outcomes. CONCLUSION: The identification of these prognostic factors is helpful for selecting the candidates for surgical treatment. Those with younger age, smaller hematoma without rostrocaudal extension, unilateral hemorrhage, and higher GCS score may benefit from surgery.

Management Strategy of a Transorbital Penetrating Pontine Injury by a Wooden Chopstick.

BACKGROUND: Transorbital penetrating pontine injuries from small spear-like objects, which are extremely rare, provide neurosurgeons with life-threatening and challenging conditions to manage. CASE DESCRIPTION: We present an unusual case of transorbital penetrating pontine injury and discuss imaging, diagnosis, management strategy, and anatomy-injury correlation. A 23-year-old man sustained a penetrating cranial injury from a bamboo chopstick that extended from the right orbit to the pons and cerebellum. Using a frontotemporal approach, we successfully removed the chopstick. Follow-up studies confirmed a good outcome. CONCLUSIONS: Preoperative imaging, correct diagnosis, and surgical treatment are necessary to manage transorbital penetrating pontine injuries caused by spear-like objects, with specific attention paid to effective exposure and inventive means with total removal of the foreign object without causing further injury. A trajectory through the superior orbital fissure and paralateral to the cavernous sinus and into the pons seems to be the most prevalent and influences management of removal and injuries.

Unilateral gunshot wound of the pons: clinical, electrophysiologic, and neuroradiologic correlates.

Following a gunshot wound to the face, a 17-year-old male patient experienced a right trigeminal and abducens paralysis, dysarthria, right-sided ataxia, left-sided weakness of the lower part of the face and limbs, and left-sided sensory loss from his neck down. Brainstem auditory evoked potentials showed a decreased P5/P1 amplitude ratio for left ear presentation, and inconsistent replication of P2 and P3 on the right and, to a lesser extent, on left ear click presentations. A computerized tomography scan showed right pontine atrophy. These findings point to a unilateral lesion of the right pons.