Reversal of neurological deficit with naloxone: an additional report

The left-right side-specific endocrine signaling in the effects of brain lesions: questioning of the neurological dogma

Each cerebral hemisphere is functionally connected to the contralateral side of the body through the decussating neural tracts. The crossed neural pathways set a basis for contralateral effects of brain injury such hemiparesis and hemiplegia as it has been already noted by Hippocrates. Recent studies demonstrated that, in addition to neural mechanisms, the contralateral effects of brain lesions are mediated through the humoral pathway by neurohormones that produce either the left or right side-specific effects. The side-specific humoral signaling defines whether the left or right limbs are affected after a unilateral brain injury. The hormonal signals are released by the pituitary gland and may operate through their receptors that are lateralized in the spinal cord and involved in the side-specific control of symmetric neurocircuits innervating the left and right limbs. Identification of features and a proportion of neurological deficits transmitted by neurohormonal signals vs. those mediated by neural pathways is essential for better understanding of mechanisms of brain trauma and stroke and development of new therapies. In a biological context, the left–right side-specific neuroendocrine signaling may be fundamental for the control of the left- and right-sided processes in bilaterally symmetric animals.

Left-right side-specific endocrine signaling complements neural pathways to mediate acute asymmetric effects of brain injury

Brain injuries can interrupt descending neural pathways that convey motor commands from the cortex to spinal motoneurons. Here, we demonstrate that a unilateral injury of the hindlimb sensorimotor cortex of rats with completely transected thoracic spinal cord produces hindlimb postural asymmetry with contralateral flexion and asymmetric hindlimb withdrawal reflexes within 3 hr, as well as asymmetry in gene expression patterns in the lumbar spinal cord. The injury-induced postural effects were abolished by hypophysectomy and were mimicked by transfusion of serum from animals with brain injury. Administration of the pituitary neurohormones β-endorphin or Arg-vasopressin-induced side-specific hindlimb responses in naive animals, while antagonists of the opioid and vasopressin receptors blocked hindlimb postural asymmetry in rats with brain injury. Thus, in addition to the well-established involvement of motor pathways descending from the brain to spinal circuits, the side-specific humoral signaling may also add to postural and reflex asymmetries seen after brain injury.

Left-Right Side-Specific Neuropeptide Mechanism Mediates Contralateral Responses to a Unilateral Brain Injury

Neuropeptides are implicated in control of lateralized processes in the brain. A unilateral brain injury (UBI) causes the contralesional sensorimotor deficits. To examine whether opioid neuropeptides mediate UBI induced asymmetric processes we compared effects of opioid antagonists on the contralesional and ipsilesional hindlimb responses to the left-sided and right-sided injury in rats. UBI induced hindlimb postural asymmetry (HL-PA) with the contralesional hindlimb flexion, and activated contralesional withdrawal reflex of extensor digitorum longus (EDL) evoked by electrical stimulation and recorded with EMG technique. No effects on the interossei (Int) and peroneaus longus (PL) were evident. The general opioid antagonist naloxone blocked postural effects, did not change EDL asymmetry while uncovered cryptic asymmetry in the PL and Int reflexes induced by UBI. Thus, the spinal opioid system may either mediate or counteract the injury effects. Strikingly, effects of selective opioid antagonists were the injury side-specific. The μ-antagonist β-funaltrexamine (FNA) and κ-antagonist nor-binaltorphimine (BNI) reduced postural asymmetry after the right but not left UBI. In contrast, the δ-antagonist naltrindole (NTI) inhibited HL-PA after the left but not right-side brain injury. The opioid gene expression and opioid peptides were lateralized in the lumbar spinal cord, and coordination between expression of the opioid and neuroplasticity-related genes was impaired by UBI that together may underlie the side-specific effects of the antagonists. We suggest that mirror-symmetric neural circuits that mediate effects of left and right brain injury on the contralesional hindlimbs are differentially controlled by the lateralized opioid system.

Ipsilesional versus contralesional postural deficits induced by unilateral brain trauma: a side reversal by opioid mechanism

Unilateral traumatic brain injury and stroke result in asymmetric postural and motor deficits including contralateral hemiplegia and hemiparesis. In animals, a localized unilateral brain injury recapitulates the human upper motor neuron syndrome in the formation of hindlimb postural asymmetry with contralesional limb flexion and the asymmetry of hindlimb nociceptive withdrawal reflexes. The current view is that these effects are developed due to aberrant activity of motor pathways that descend from the brain into the spinal cord. These pathways and their target spinal circuits may be regulated by local neurohormonal systems that may also mediate effects of brain injury. Here, we evaluate if a unilateral traumatic brain injury induces hindlimb postural asymmetry, a model of postural deficits, and if this asymmetry is spinally encoded and mediated by the endogenous opioid system in rats. A unilateral right-sided controlled cortical impact, a model of clinical focal traumatic brain injury was centred over the sensorimotor cortex and was observed to induce hindlimb postural asymmetry with contralateral limb flexion. The asymmetry persisted after complete spinal cord transection, implicating local neurocircuitry in the development of the deficits. Administration of the general opioid antagonist naloxone and μ-antagonist β-funaltrexamine blocked the formation of postural asymmetry. Surprisingly, κ-antagonists nor-binaltorphimine and LY2444296 did not affect the asymmetry magnitude but reversed the flexion side; instead of contralesional (left) hindlimb flexion the ipsilesional (right) limb was flexed. The postural effects of the right-side cortical injury were mimicked in animals with intact brain via intrathecal administration of the opioid κ-agonist (2)-(trans)-3,4-Dichloro-N-methyl-N-[2-(1-pyrrolidiny)-cyclohexyl]benzeneacetamide that induced hindlimb postural asymmetry with left limb flexion. The δ-antagonist naltrindole produced no effect on the contralesional (left) flexion but inhibited the formation of the ipsilesional (right) limb flexion in brain-injured rats that were treated with κ-antagonist. The effects of the antagonists were evident before and after spinal cord transection. We concluded that the focal traumatic brain injury-induced postural asymmetry was encoded at the spinal level, and was blocked or its side was reversed by administration of opioid antagonists. The findings suggest that the balance in activity of the mirror symmetric spinal neural circuits regulating contraction of the left and right hindlimb muscles is controlled by different subtypes of opioid receptors; and that this equilibrium is impaired after unilateral brain trauma through side-specific opioid mechanism.

Recrudescence of Old Stroke Deficits Among Transient Neurological Attacks

Background

Recrudescence of old stroke deficits (ROSD) is a reported cause of transient neurological symptoms, but it is not well characterized.

Objective

We sought to determine the prevalence, potential triggers, and clinical outcome of ROSD in a cohort of patients presenting with acute transient neurological attack (TNA) and absent acute pathology on brain imaging.

Methods

We retrospectively analyzed 340 consecutive patients who presented with TNA and no acute pathology on brain imaging that were included in an institutional stroke registry between February 2013 and April 2015. The presumed TNA cause was categorized as transient ischemic attack (TIA), ROSD, and other cause. Baseline characteristics, triggers, cardiovascular complications within 90 days, and death were recorded.

Results

The prevalence of ROSD in the studied cohort was 10% (34/340). Infectious stressors and acute metabolite derangements were more common in ROSD compared to TIA (P < .05, each). Compared to TIA and the other TNA, ROSD was more likely to have more than 1 acute stressor (P < .001). Patients with ROSD had similar vascular risk factors compared to TIA (P > .05), including hypertension, diabetes mellitus, peripheral vascular disease, hyperlipidemia, and similarly used HMG-CoA reductase inhibitor, antihypertensive, and antiplatelet medications. Among the patients with an available 90-day follow-up (n = 233), cardiovascular events were more frequent in the TIA group as compared to other TNA (P < .05).

Conclusion

ROSD is common and distinct from TIA and is associated with a triggering physiologic reaction leading to transient reemergence of prior neurologic deficits. Further study of the mechanism of this phenomenon is needed to help better identify these patients.

Recrudescence of Focal Stroke Symptoms during Pain Management with Hydromorphone

Patients who have recovered from a prior stroke may experience a reemergence of their original stroke syndrome secondary to metabolic derangements, sedation, infection, and/or fatigue. Critically, the molecular/cellular mechanisms mediating symptom recurrence after exposure to analgesic agents remain unknown. Accordingly, herein, we report a unique case of a patient with hydromorphone-induced recrudescence 30 years after her initial stroke event(s) and in so doing propose a putative mechanism related to post-infarction functional neuroplasticity.

Transient anesthetic-induced worsening of existing left-sided weakness in a patient undergoing elective anterior cervical discectomy

The differential diagnosis of new or worsening focal neurologic deficits on emergence from anesthesia is broad. Cerebral ischemia or hemorrhage, focal seizures, and acute metabolic abnormalities can all result in similar neurologic findings. Intravenously administered anesthetic agents also have been reported to cause new or worsening focal neurologic deficits in patients with a history of preexisting deficits. A patient who suffered such a reversible deficit related to anesthesia is presented.

Awakening management after neurosurgery for intracranial tumours

PURPOSE OF REVIEW

Major complications after intracranial surgery occur in 13-27% of patients. These complications may have multiple causes, but a body of arguments suggests that the haemodynamic and metabolic changes of anaesthesia recovery may be responsible for intracranial complications. The aim of this review is to explain the rationale of this hypothesis and analyse the recent studies relevant to neuroanaesthesia recovery.

RECENT FINDINGS

Rapid recovery and extubation after intracranial tumour surgery is desirable in order to make an early diagnosis of intracranial complications. Since light pharmacological sedation may worsen a neurological deficit, short-acting anaesthetics are preferable intraoperatively. Extubation in the operating room, however, may be associated with agitation, increased oxygen consumption, catecholamine secretion, hypercapnia and systemic hypertension. This may exacerbate cerebral hyperaemia observed even during an uneventful recovery, leading to cerebral oedema or haemorrhage.

SUMMARY

Pain, hypothermia, hypercapnia, hypoxia, hypoosmolality, hypertension, and anaemia should be avoided during emergence. Early emergence is associated with minimal haemodynamic and metabolic changes. If there is any doubt as to whether the patient should be extubated in the operating room, a gradual emergence in the intensive care unit makes it possible to decide whether or not extubation can be performed safely.