Neurocoagulation from a Mechanistic Point of View in the Central Nervous System

Coagulation mechanisms are critical for maintaining homeostasis in the central nervous system (CNS). Thrombin, an important player of the coagulation cascade, activates protease activator receptors (PARs), members of the G-protein coupled receptor family. PAR1 is located on neurons and glia. Following thrombin activation, PAR1 signals through the extracellular signal-regulated kinase pathway, causing alterations in neuronal glutamate release and astrocytic morphological changes. Similarly, the anticoagulation factor activated protein C (aPC) can cleave PAR1, following interaction with the endothelial protein C receptor. Both thrombin and aPC are expressed on endothelial cells and pericytes in the blood-brain barrier (BBB). Thrombin-induced PAR1 activation increases cytosolic Ca²⁺ concentration in brain vessels, resulting in nitric oxide release and increasing F-actin stress fibers, damaging BBB integrity. aPC also induces PAR1 activation and preserves BBB vascular integrity via coupling to sphingosine 1 phosphate receptors. Thrombin-induced PAR1 overactivation and BBB disruption are evident in CNS pathologies. During epileptic seizures, BBB disruption promotes thrombin penetration. Thrombin induces PAR1 activation and potentiates N-methyl-D-aspartate receptors, inducing glutamate-mediated hyperexcitability. Specific PAR1 inhibition decreases status epilepticus severity in vivo. In stroke, the elevation of brain thrombin levels further compromises BBB integrity, with direct parenchymal damage, while systemic factor Xa inhibition improves neurological outcomes. In multiple sclerosis (MS), brain thrombin inhibitory capacity correlates with clinical presentation. Both thrombin inhibition by hirudin and the use of recombinant aPC improve disease severity in an MS animal model. This review presents the mechanisms underlying the effects of coagulation on the physiology and pathophysiology of the CNS.

Thrombin as Key Mediator of Seizure Development Following Traumatic Brain Injury

Traumatic brain injury (TBI) commonly leads to development of seizures, accounting for approximately 20% of newly diagnosed epilepsy. Despite the high clinical significance, the mechanisms underlying the development of posttraumatic seizures (PTS) remain unclear, compromising appropriate management of these patients. Accumulating evidence suggest that thrombin, the main serine protease of the coagulation cascade, is involved in PTS genesis by mediating inflammation and hyperexcitability following blood brain barrier breakdown. In order to further understand the role of thrombin in PTS, we generated a combined mild TBI (mTBI) and status epilepticus mice model, by injecting pilocarpine to mice previously submitted to head injury. Interestingly, mTBI was able to reduce seizure onset in the pilocarpine animal model as well as increase the death rate in the treated animals. In turn, pilocarpine worsened spatial orientation of mTBI treated mice. Finally, thrombin activity as well as the expression of IL1-β and TNF-α was significantly increased in the mTBI-pilocarpine treated animals. In conclusion, these observations indicate a synergism between thrombin and mTBI in lowering seizure in the pilocarpine model and possibly aggravating inflammation. We believe that these results will improve the understanding of PTS pathophysiology and contribute to the development of more targeted therapies in the future.

Post Stroke Seizures and Epilepsy: From Proteases to Maladaptive Plasticity

Post stroke epilepsy (PSE) is the most common cause of seizures in the elderly, yet its underlying mechanism is poorly understood. The classification of PSE is confusing, and there is neither a clear agreement on its incidence and prognosis nor a consensus about specific treatments. The diagnosis of PSE requires the occurrence of late seizures: epileptic events occurring 1 week or more after an ischemic stroke. Late seizures differ from early seizures by the presence of permanent structural changes in the brain. Those structural changes cause a shift in the regulation of neuronal firing and lead to circuit dysfunctions, and thus to a long-term epileptic condition. The coagulation cascade and some of its major components, serine proteases such as thrombin, are known to participate in the acute phase of a stroke. Recent discoveries found that thrombin and its protease-activated receptor 1 (PAR1), are involved in the development of maladaptive plasticity. Therefore, we suggest that thrombin and PAR1 may have a role in the development of PSE by inducing permanent structural changes after the ischemic events toward the development of epileptic focuses. We are confident that future studies will lead to a better understanding of the pathophysiology of PSE, as well as development of more directed therapies for its treatment.

Ocular palsy following Le Fort 1 osteotomy: a case report

A 33-year-old female patient developed an ipsilateral sixth nerve palsy and partial third nerve palsy following a Le Fort 1 osteotomy. Complete resolution occurred at 10 weeks. The likely mechanism of injury secondary to pterygo-maxillary dysjunction is highlighted, with description of the relevant anatomy. Previous cases of ocular motility complications following Le Fort 1 osteotomy are discussed. We recommend that significant care be taken in osteotome placement in the pterygo-maxillary fissure, particularly in those prone to unpredicted fractures such as older patients, or where the anatomy is congenitally abnormal or altered by previous surgery.

An assessment of the aggressive potential of radiolucencies related to the mandibular molar teeth

AIM

The purpose of this study was to outline the radiographic appearance of radiolucent lesions related to the molar teeth and to determine which features indicate aggressive lesions.

PATIENTS AND METHODS

Panoramic radiographs were reviewed in 66 patients with radiolucencies related to the molar teeth. The radiographic appearances of the lesions were assessed with regard to location and size, and the relationship to the molar teeth. Radiographic evidence of aggression was assessed and pathology reviewed.

RESULTS

Nineteen patients had aggressive and 47 had non-aggressive radiolucent lesions. The aggressive lesions included keratocysts, unicystic ameloblastoma, adenoid cystic carcinoma, giant cell granuloma, myxofibroma, chondroblastic osteosarcoma, mestastases and squamous cell carcinoma of the tongue invading the mandible.

CONCLUSION

The differential diagnosis of radiolucent lesions in the mandible can be difficult using panoramic radiographs alone. Helpful features in determining aggression were older patients, larger lesions, Lodwick type IC tumour border, condition of the mandibular cortex, movement of adjacent teeth and the relationship of the inferior alveolar canal.

Reconstruction techniques in oral carcinoma

Resection of oral carcinoma can cause serious problems with speech, mastication and swallowing. Several methods of reconstruction of the defects caused by tumour resection are available to the modern oral and maxillofacial/head and neck surgeon, some of which are more effective and aesthetically pleasing than others. This article discusses the methods available, their advantages and disadvantages, and gives guidelines on the circumstances in which each is ideally used.

Non-union of mandibulotomy sites following irradiation for squamous cell carcinoma of the oral cavity

Mandibulotomy improves surgical access to the oral cavity for the resection of tumours. Non-union of the mandibulotomy due to osteoradionecrosis has been observed in five patients with oral squamous cell carcinoma, all of whom had radiotherapy either as the primary modality of treatment or for tumour recurrence. This paper reports this series of patients, discusses their management and highlights the risk factors for the development of osteoradionecrosis.

Lidocaine in refractory status epilepticus: confirmation of efficacy with continuous EEG monitoring

Lidocaine was efficacious in 2 patients with refractory status epilepticus (RSE) unresponsive to several antiepileptic drugs (AEDs), including high-dose barbiturates. We confirmed the efficacy of lidocaine with, for the first time in adults, continuous EEG monitoring. Lidocaine, when properly used, may be a treatment option in RSE.

Merkel cell carcinoma

A case of Merkel cell carcinoma of the cheek is described, highlighting the clinical behaviour, diagnosis and management of this uncommon tumour.

Bone scans and the timing of treatment for condylar hyperplasia

Bone scintiscans comparing the uptake of technetium 99 in the normal and affected condyles of 10 patients with unilateral condylar hyperplasia were recorded at or after the time when overall growth had ceased. The scans of 6 patients demonstrated persisting increased growth activity at this time. In 2 of these cases where the abnormal condyles showed uptakes of 240% and 170% with respect to the normal side, the nature and timing of treatment were changed when the results of the scans were known.

The Marcus Gunn (jaw-winking) phenomenon: a case report

The clinical features of the Marcus Gunn (jaw-winking) phenomenon are described and a case is reported in a 23-year-old female who also had congenital left duplex kidneys and ureters.

Nuclear imaging and the assessment of human Fc receptor function: studies in systemic lupus erythematosus

In vivo immune clearance of immunoglobulin G sensitized autologous erythrocytes (rbc) was studied in nine patients who fulfilled American Rheumatism Association (ARA) criteria for systemic lupus erythematosus (SLE). Opsonized rbc were radiolabelled with technetium 99. The rate of radioactive blood clearance was measured, as was organ-specific radioactive uptake utilizing area-of-interest (AOI) measurements in a computerized scintigraphic imaging system. It was shown that dynamic quantitation of an AOI corresponding to the heart generated time-activity curves which approximated blood-clearance curves. Calculation of first order clearance (min per 50% decrease in counts) showed a highly significant correlation between rates derived from heart AOI curves and those derived from blood-clearance curves (r = 0.9483, P = 0.0003). Clearance curves showed a monoexponential slope in most patients. Further exploration of organ-specific AOI curves showed that percent splenic uptake and the nature of the splenic uptake curves varied between patients. These studies point toward a variable splenic role in Fc receptor function for SLE patients and further demonstrate the utility of nuclear imaging in studying immune clearance.

Central cervical spinal cord syndrome due to minor hyperextension injury

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A survey of surgical rotations for oral & maxillofacial surgery trainees

Seventy oral and maxillofacial surgery departments were sent questionnaires to determine whether they made provision for their medically qualified registrars to undergo 1 year's surgical training in recognition for the Part II FRCS oral and maxillofacial surgery option of the Royal College of Surgeons of Edinburgh. Fifty-six (80%) replies were received revealing that 11 (19.6%) departments had existing arrangements for a surgical rotation while 14 (25%) had plans to implement one. These results are further reported.

Training graduate students in parent conference skills

Twelve graduate students were trained in three categories of parent conference skills: communicating diagnostic information, communicating recommendations, and organizing the conference and interacting with parents. Training done individually with each student consisted of written programmed learning materials plus oral practice. Training effects were measured during role-play and actual parent conferences. Training effectiveness was assessed with a multiple baseline design across three skill categories. Eleven of 12 students exhibited significant skill acquisition and nine generalized skills to an actual parent conference. Professionals and parents of developmentally delayed children attested to the importance and effectiveness of the training program. Results demonstrated that parent conference skills can be operationalized, trained, and generalized to actual conferences.

Suppressing aggressive-destructive behavior by delayed overcorrection

Delayed overcorrection reduced the aggressive-destructive behavior of a developmentally delayed adolescent when it was added to previously ineffective procedures of differential reinforcement (tokens and token-removal) of other behavior. The delayed contingency was necessary because target behaviors occurred exclusively in the absence of the only family member who could overpower the subject. A multiple baseline design across two levels of problem-behavior severity indicated that delayed overcorrection effectively suppressed the aggressive-destructive episodes. The results support the notion that delayed contingencies can effectively suppress target behaviors.

Modifying the self-injurious behavior of an infant with spina bifida and diminished pain sensitivity

This clinical case study extends the literature on behavioral treatment of self-injury to an intellectually normal infant with spina bifida and diminished sensitivity to pain. After treatment by attention-play periods plus an aversive tasting substance applied to the injured finger, severe biting of the index finger was eliminated and the finger healed. Follow-up inquiries 2 months, 2 and 3 yr later revealed no biting and no substantial tissue damage.

Treatment of unobserved trichotillomania by attention-reflection and punishment of an apparent covariant

Frequent but primarily unobserved hairpulling, by a 3-yr-old girl was followed by a differential reinforcement procedure, attention-reflection, and punishment of thumbsucking, a possibly covarying behavior. Initially, attention-reflection reduced the hairpulling, but not to a clinically significant level. Dramatic decreases in hairpulling were achieved when thumbsucking was punished by application of a "bad tasting" substance. A brief reversal supports the contention that the two behaviors were correlated and suggests that behaviors may be controlled by targeting observable covariants.

Suppression of self-injurious behaviour: determining the least restrictive alternative

In keeping with recent ethical and legal guidelines regarding the use of aversive treatment procedures, a number of alternatives for the treatment of self-injury have been suggested. The present study provides an example of the determination of the least restrictive but most effective treatment with a case of self-injury. Employing a combination of multiple baseline and reversal designs, the effects of DRO, overcorrection, lemon juice, and aromatic ammonia on the rate of self-poking in a profoundly retarded child were examined. DRO and overcorrection were both ineffective. Although lemon juice suppressed and stabilised the rate of poking, aromatic ammonia produced greater suppression. Implications for the testing of treatments for SIB are discussed.

Effects of the Feingold diet on seizures and hyperactivity: a single-subject analysis

The effects of a dietary manipulation on seizure frequency and activity level of a 3 1/2-year-old male with tuberous sclerosis, mental retardation, and uncontrolled seizures were assessed. Using a reversal design, the Feingold (K-P) diet was presented and withdrawn three times, while the medication regimen remained unaltered. Every application of the K-P diet resulted in substantial reductions in seizure frequency. During a 21-week follow-up, seizure frequency remained low despite the phasing out of one drug, and seizures were reportedly eliminated 1 year later. Brief objective measures of hyperactivity failed to show any effect due to the diet changes.

Behavioral treatment of obesity in patients with Prader-Willi syndrome

Self-monitoring combined with contingency contracting resulted in weight loss, modification of dysfunctional eating habits, and increased or sustained exercise rates for two obese, mentally retarded adolescent females with Prader-Willi syndrome. Contingency contracting between clients and their parents/caregivers was used to specify consequences for daily self-monitoring, reduced caloric intake, weight loss, and exercise. Punishment for food stealing was also employed. Results suggest that contingency contracting is an effective technique for producing long-term weight loss in obese mentally retarded adolescents. Further, these techniques offer an alternative to the clinician considering solely dietary restriction or surgical intervention.

Effect of progestins on androgen delta4-3-ketosteroid-5alpha-A-ring reductase system in rat oral mucosa

Rat oral mucosa microsomal delta4-3-ketosteroid-5alpha-A-ring reductase enzyme system, reducing testosterone and 4-androstenedione, was found to be inducible by systemic administration of medroxyprogesterone acetate (MPA). MPA, when used in a mixture with testosterone and/or 4-androstenedione in vitro, acted as a competitive inhibitor of the reduction of these substrates.

Specific glucocorticoid receptor in the iris--ciliary body of the rabbit

The cytoplasm of the iris--ciliary body of the rabbit contains a receptor capable of specifically binding dexamethasone. This binding protein has a high affinity for dexamethasone (average KD = 2.0 X 10(-8) M), a low capacity (average 4.8 X 10(-13) mol of steroid bound per milligram of protein), and extreme heat sensitivity; it exhibits a pattern of competition virtually identical to that obtained with glucocorticoid receptors from other tissues and shows characteristic physicochemical behavior in various salt concentrations. The demonstration of a specific dexamethasone receptor in the iris--ciliary body provides the first direct biochemical evidence that these tissues may function as a target organ for glucocorticoids.

Establishing walking by severely retarded children

This article examines the implications of independent ambulation for severely retarded children and reviews the literature describing behavioral interventions which facilitate walking. Findings from applied behavior analysis of single subjects support the value of operant techniques in the acquisition of walking. An operationally defined, data-based, four-level sequence for training walking beginning with momentary standing and ending with independent walking on command is described. Representative data from five severely retarded children are presented.

Effect of alcohol (ethanol) administration on sex-hormone metabolism in normal men

To determine whether ethanol per se affects testosterone metabolism, alcohol was administered to normal male volunteers for periods up to four weeks, resulting in an initial dampening of the episodic bursts of testosterone secretion followed by decreases in both the mean plasma concentration and the production rate of testosterone. The volunteers received adequate nutrition and none lost weight during the study, which tended to exclude a nutritional disturbance as the cause of the decreased testosterone levels. The changes in plasma luteinizing hormone suggested both a central (hypothalamus-pituitary) and gonadal effect of alcohol. In addition, alcohol consumption increased the metabolic clearance rate of testosterone in most subjects studied, probably owing to the combined effects of a decreased plasma binding capacity for the androgen and increased hepatic testosterone A-ring reductase activity. These results indicate that alcohol markedly affects testosterone metabolism independently of cirrhosis or nutritional factors.

Steroid metabolism in ocular tissues of the rabbit

The metabolism of cortisol and other steroids was studied in normal untreated rabbit iris-ciliary body and cornea as part of an investigation into the mechanism of glucocorticoid-induced glaucoma. Cortisol is readily converted to the inactive metabolite cortisone by these eye tissues indicating the presence of an 11beta-oxidoreductase system. This reaction is reversible with cortisone being converted to cortisol in the presence of appropriate cofactor. However, due to the absence of a (or as yet undetectable) cortisol-A-ring-reductase system (rate-limiting reaction) the steroid is not irreversibly metabolized to biologically inactive compounds. The 11beta-oxidoreductase system readily converts other C21-11beta-hydroxysteroids, such as corticosterone, to its appropriate C21-11-ketosteroid (11-dehydrocorticosterone). Some C21-steroids lacking the 11-hydroxyl group (11-deoxycortisol, 11-deoxycorticosterone) remain virtually unmetabolized (exception to this was found with progesterone). Evidence of a C21-steroid A-ring reductase system was found only when cortisone and progesterone were used as substrates. However, testosterone a C19 steroid was converted to clearly identifiable A-ring reduced and 17beta-and 3alpha(beta)-oxidoreduced metabolites, thus indicating the presence of testosterone A-ring reductase, 17beta-and 3alpha(beta)-oxidoreductase systems in the eye tissues studied. The presence of a steroid 5alpha(beta)-reductase for some steroids but not for cortisol indicates a distinct substrate specificity for this enzyme system in the eye tissues.

Prolonged ethanol consumption increases testosterone metabolism in the liver

Male alcoholics often suffer from features of hypogonadism related to abnormal metabolism of sex steroids. Since the activity of testosterone reductases is rate limiting for testosterone metabolism in the liver, the effect of prolonged ethanol consumption by rats and human volunteers on the activities of these microsomal and cytosolic enzymes was studied. In rats, long-term ethanol ingestion doubled microsomal 5alpha-testosterone reductase activity, a major pathway for testosterone metabolism, while in human volunteers the activity was increased two- to fivefold. These changes may play a role in the altered androgenic activity of the chronic alcoholic.