Structural, Surface and Optical Studies of m- and c-Face AlN Crystals Grown by Physical Vapor Transport Method

Bulk aluminum nitride (AlN) crystals with different polarities were grown by physical vapor transport (PVT). The structural, surface, and optical properties of m-plane and c-plane AlN crystals were comparatively studied by using high-resolution X-ray diffraction (HR-XRD), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. Temperature-dependent Raman measurements showed that the Raman shift and the full width at half maximum (FWHM) of the E₂ (high) phonon mode of the m-plane AlN crystal were larger than those of the c-plane AlN crystal, which would be correlated with the residual stress and defects in the AlN samples, respectively. Moreover, the phonon lifetime of the Raman-active modes largely decayed and its line width gradually broadened with the increase in temperature. The phonon lifetime of the Raman TO-phonon mode was changed less than that of the LO-phonon mode with temperature in the two crystals. It should be noted that the influence of inhomogeneous impurity phonon scattering on the phonon lifetime and the contribution to the Raman shift came from thermal expansion at a higher temperature. In addition, the trend of stress with increasing 1000/temperature was similar for the two AlN samples. As the temperature increased from 80 K to ~870 K, there was a temperature at which the biaxial stress of the samples transformed from compressive to tensile stress, while their certain temperature was different.

Synthesis, Structural and Magnetic Properties of Cobalt-Doped GaN Nanowires on Si by Atmospheric Pressure Chemical Vapor Deposition

GaN nanowires (NWs) grown on silicon via atmospheric pressure chemical vapor deposition were doped with Cobalt (Co) by ion implantation, with a high dose concentration of 4 × 10¹⁶ cm^-2, corresponding to an average atomic percentage of ~3.85%, and annealed after the implantation. Co-doped GaN showed optimum structural properties when annealed at 700 °C for 6 min in NH₃ ambience. From scanning electron microscopy, X-ray diffraction, high resolution transmission electron microscope, and energy dispersive X-ray spectroscopy measurements and analyses, the single crystalline nature of Co-GaN NWs was identified. Slight expansion in the lattice constant of Co-GaN NWs due to the implantation-induced stress effect was observed, which was recovered by thermal annealing. Co-GaN NWs exhibited ferromagnetism as per the superconducting quantum interference device (SQUID) measurement. Hysteretic curves with Hc (coercivity) of 502.5 Oe at 5 K and 201.3 Oe at 300 K were obtained. Applied with a magnetic field of 100 Oe, the transition point between paramagnetic property and ferromagnetic property was determined at 332 K. Interesting structural and conducive magnetic properties show the potential of Co-doped GaN nanowires for the next optoelectronic, electronic, spintronic, sensing, optical, and related applications.

Angle-Dependent Raman Scattering Studies on Anisotropic Properties of Crystalline Hexagonal 4H-SiC

Raman scattering spectroscopy (RSS) has the merits of non-destructiveness, fast analysis, and identification of SiC polytype materials. By way of angle-dependent Raman scattering (ADRS), the isotropic characteristics are confirmed for c-face 4H-SiC, while the anisotropic properties of a-face 4H-SiC are revealed and studied in detail via combined experiments and theoretical calculation. The variation functional relationship of the angle between the incident laser polarization direction and the parallel (perpendicular) polarization direction was well established. The selection rules of wurtzite 4H-SiC are deduced, and the intensity variations of the A₁, E_2, and E₁ Raman phonon modes dependent on the incident angle are calculated, and well-matched with experimental data. Raman tensor elements of various modes are determined.

Strain-stress study of AlxGa1-xN/AlN heterostructures on c-plane sapphire and related optical properties

This work presents a systematic study of stress and strain of Al_xGa_1−xN/AlN with composition ranging from GaN to AlN, grown on a c-plane sapphire by metal-organic chemical vapor deposition, using synchrotron radiation high-resolution X-ray diffraction and reciprocal space mapping. The c-plane of the Al_xGa_1−xN epitaxial layers exhibits compressive strain, while the a-plane exhibits tensile strain. The biaxial stress and strain are found to increase with increasing Al composition, although the lattice mismatch between the Al_xGa_1−xN and the buffer layer AlN gets smaller. A reduction in the lateral coherence lengths and an increase in the edge and screw dislocations are seen as the Al_xGa_1−xN composition is varied from GaN to AlN, exhibiting a clear dependence of the crystal properties of Al_xGa_1−xN on the Al content. The bandgap of the epitaxial layers is slightly lower than predicted value due to a larger tensile strain effect on the a-axis compared to the compressive strain on the c-axis. Raman characteristics of the Al_xGa_1−xN samples exhibit a shift in the phonon peaks with the Al composition. The effect of strain on the optical phonon energies of the epitaxial layers is also discussed.

N-Terminal pro-Brain Natriuretic Peptide and Associations With Brain Magnetic Resonance Imaging (MRI) Features in Middle Age: The CARDIA Brain MRI Study

Objective

As part of research on the heart–brain axis, we investigated the association of N-terminal pro-brain natriuretic peptide (NT-proBNP) with brain structure and function in a community-based cohort of middle-aged adults from the Brain Magnetic Resonance Imaging sub-study of the Coronary Artery Risk Development in Young Adults (CARDIA) Study.

Approach and results

In a cohort of 634 community-dwelling adults with a mean (range) age of 50.4 (46–52) years, we examined the cross-sectional association of NT-proBNP to total, gray (GM) and white matter (WM) volumes, abnormal WM load and WM integrity, and to cognitive function tests [the Digit Symbol Substitution Test (DSST), the Stroop test, and the Rey Auditory–Verbal Learning Test]. These associations were examined using linear regression models adjusted for demographic and cardiovascular risk factors and cardiac output. Higher NT-proBNP concentration was significantly associated with smaller GM volume (β = −3.44; 95% CI = −5.32, −0.53; p = 0.003), even after additionally adjusting for cardiac output (β = −2.93; 95% CI = −5.32, −0.53; p = 0.017). Higher NT-proBNP levels were also associated with lower DSST scores. NT-proBNP was not related to WM volume, WM integrity, or abnormal WM load.

Conclusion

In this middle-aged cohort, subclinical levels of NT-proBNP were related to brain function and specifically to GM and not WM measures, extending similar findings in older cohorts. Further research is warranted into biomarkers of cardiac dysfunction as a target for early markers of a brain at risk.

Association Between Partial Pressure of Arterial Carbon Dioxide and Survival to Hospital Discharge Among Patients Diagnosed With Sepsis in the Emergency Department

OBJECTIVE

The objective of this study was to test the association between the partial pressure of arterial carbon dioxide and survival to hospital discharge among mechanically ventilated patients diagnosed with sepsis in the emergency department.

DESIGN

Retrospective cohort study of a single center trial registry.

SETTING

Academic medical center.

PATIENTS

Mechanically ventilated emergency department patients.

INCLUSION CRITERIA

age 18 years and older, diagnosed with sepsis in the emergency department, and mechanical ventilation initiated in the emergency department.

INTERVENTIONS

Arterial blood gases obtained after initiation of mechanical ventilation were analyzed. The primary outcome was survival to hospital discharge. We tested the association between partial pressure of arterial carbon dioxide and survival using multivariable logistic regression adjusting for potential confounders. Sensitivity analyses, including propensity score matching were also performed.

MEASUREMENTS AND MAIN RESULTS

Six hundred subjects were included, and 429 (72%) survived to hospital discharge. The median (interquartile range) partial pressure of arterial carbon dioxide was 42 (34-53) mm Hg for the entire cohort and 44 (35-57) and 39 (31-45) mm Hg among survivors and nonsurvivors, respectively (p < 0.0001 Wilcox rank-sum test). On multivariable analysis, a 1 mm Hg rise in partial pressure of arterial carbon dioxide was associated with a 3% increase in odds of survival (adjusted odds ratio, 1.03; 95% CI, 1.01-1.04) after adjusting for tidal volume and other potential confounders. These results remained significant on all sensitivity analyses.

CONCLUSION

In this sample of mechanically ventilated sepsis patients, we found an association between increasing levels of partial pressure of arterial carbon dioxide and survival to hospital discharge. These findings justify future studies to determine the optimal target partial pressure of arterial carbon dioxide range for mechanically ventilated sepsis patients.

Partial pressure of arterial carbon dioxide and survival to hospital discharge among patients requiring acute mechanical ventilation: A cohort study

PURPOSE

To describe the prevalence of hypocapnia and hypercapnia during the earliest period of mechanical ventilation, and determine the association between PaCO2 and mortality.

MATERIALS AND METHODS

A cohort study using an emergency department registry of mechanically ventilated patients. PaCO2 was categorized: hypocapnia (<35mmHg), normocapnia (35-45mmHg), and hypercapnia (>45mmHg). The primary outcome was survival to hospital discharge.

RESULTS

A total of 1,491 patients were included. Hypocapnia occurred in 375 (25%) patients and hypercapnia in 569 (38%). Hypercapnia (85%) had higher survival rate compared to normocapnia (74%) and hypocapnia (66%), P<0.001. PaCO2 was an independent predictor of survival to hospital discharge [hypocapnia (aOR 0.65 (95% confidence interval [CI] 0.48-0.89), normocapnia (reference category), hypercapnia (aOR 1.83 (95% CI 1.32-2.54)]. Over ascending ranges of PaCO2, there was a linear trend of increasing survival up to a PaCO2 range of 66-75mmHg, which had the strongest survival association, aOR 3.18 (95% CI 1.35-7.50).

CONCLUSIONS

Hypocapnia and hypercapnia occurred frequently after initiation of mechanical ventilation. Higher PaCO2 levels were associated with increased survival. These data provide rationale for a trial examining the optimal PaCO2 in the critically ill.

Lung-Protective Ventilation Initiated in the Emergency Department (LOV-ED): A Quasi-Experimental, Before-After Trial

STUDY OBJECTIVE

We evaluated the efficacy of an emergency department (ED)-based lung-protective mechanical ventilation protocol for the prevention of pulmonary complications.

METHODS

This was a quasi-experimental, before-after study that consisted of a preintervention period, a run-in period of approximately 6 months, and a prospective intervention period. The intervention was a multifaceted ED-based mechanical ventilator protocol targeting lung-protective tidal volume, appropriate setting of positive end-expiratory pressure, rapid oxygen weaning, and head-of-bed elevation. A propensity score-matched analysis was used to evaluate the primary outcome, which was the composite incidence of acute respiratory distress syndrome and ventilator-associated conditions.

RESULTS

A total of 1,192 patients in the preintervention group and 513 patients in the intervention group were included. Lung-protective ventilation increased by 48.4% in the intervention group. In the propensity score-matched analysis (n=490 in each group), the primary outcome occurred in 71 patients (14.5%) in the preintervention group compared with 36 patients (7.4%) in the intervention group (adjusted odds ratio 0.47; 95% confidence interval [CI] 0.31 to 0.71). There was an increase in ventilator-free days (mean difference 3.7; 95% CI 2.3 to 5.1), ICU-free days (mean difference 2.4; 95% CI 1.0 to 3.7), and hospital-free days (mean difference 2.4; 95% CI 1.2 to 3.6) associated with the intervention. The mortality rate was 34.1% in the preintervention group and 19.6% in the intervention group (adjusted odds ratio 0.47; 95% CI 0.35 to 0.63).

CONCLUSION

Implementing a mechanical ventilator protocol in the ED is feasible and is associated with significant improvements in the delivery of safe mechanical ventilation and clinical outcome.

Genome Modeling System: A Knowledge Management Platform for Genomics

In this work, we present the Genome Modeling System (GMS), an analysis information management system capable of executing automated genome analysis pipelines at a massive scale. The GMS framework provides detailed tracking of samples and data coupled with reliable and repeatable analysis pipelines. The GMS also serves as a platform for bioinformatics development, allowing a large team to collaborate on data analysis, or an individual researcher to leverage the work of others effectively within its data management system. Rather than separating ad-hoc analysis from rigorous, reproducible pipelines, the GMS promotes systematic integration between the two. As a demonstration of the GMS, we performed an integrated analysis of whole genome, exome and transcriptome sequencing data from a breast cancer cell line (HCC1395) and matched lymphoblastoid line (HCC1395BL). These data are available for users to test the software, complete tutorials and develop novel GMS pipeline configurations. The GMS is available at https://github.com/genome/gms.

Device design and simulation for GaN based dual wavelength LEDs

A comprehensive optical model for dual wavelength LEDs is developed using optical ray tracing programs. Optical dispersion of GaN, InGaN, and AlGaN is also included in this numerical model. The light extraction efficiency of LEDs can be calculated based on LED structure and material properties. Moreover, a LED device structure can be optimized to improve the light extraction efficiency.

Simultaneous detection of ultraviolet and infrared radiation in a single GaN/GaAlN heterojunction

Results are presented for a dual-band detector that simultaneously detects UV radiation in the 250-360 nm and IR radiation in the 5-14 microm regions with near zero spectral cross talk. In this detector having separate UV- and IR-active regions with three contacts (one common contact for both regions) allows the separation of the UV and IR generated photocurrent components, identifying the relative strength of each component. This will be an important development in UV-IR dual-band applications such as fire-flame detection, solar astronomy, and military sensing, eliminating the difficulties of employing several individual detectors with separate electronics-cooling mechanisms.

GaN-based distributed Bragg reflector for high-brightness LED and solid-state lighting

A comprehensive numerical model for distributed Bragg reflectors (DBRs) based on thin-film optics is developed. Detailed refractive-index calculations for GaN, AlN, AlGaN, and InGaN can also be included in this numerical model. This model can predict DBR performances for refractive-index variations, layer-thickness fluctuations, and the number of quarter-wave stack pairs in DBR as well different light polarizations.

Irreversible damage to the spinal cord following spinal anesthesia

The authors report five patients with damage to the distal spinal cord following spinal anesthesia. The patients developed leg weakness and sensory disturbance. MRI of the lumbosacral spine showed an abnormal area of high signal within the conus medullaris in all patients. Symptoms and signs persisted at 1- to 2.5-year follow-ups. Incorrect needle placement and type of needle used are possible factors leading to spinal cord injury.

Evidence for interactive locomotor and oculomotor deficits in cerebellar patients during visually guided stepping

Eight patients suffering from primary cerebellar degenerative diseases undertook a walkway task, demanding precise foot placement at each step, and a visual fixation task, requiring only eye movements. Step cycle and horizontal eye movements were recorded throughout the tasks and compared to those of healthy adults (including age- and sex-matched controls). Cerebellar patients displayed both locomotor and oculomotor deficits. Increases in duration of the stance, swing and double support phases of the step cycle were all shown to contribute to ataxic gait. Dysmetric saccades to fixate the footfall targets were seen more frequently in patients than in controls. These hypometric saccades were followed by one or more corrective saccades (patients: >45% accompanied by one or more corrective saccades; controls: <10% accompanied by a single corrective saccade). Similarities between the oculomotor deficits displayed by patients during the visual fixation task and when walking indicate that the latter are not merely a consequence of ataxic gait. The existence of several links between these locomotor and oculomotor deficits provides evidence for considerable interaction between the two control systems in the production of patterned eye and stepping movements. These results also suggest that the cerebellum plays an active role in the co-ordination of visually guided eye and limb movements during visually guided stepping.

Parkinsonism associated with obstructive hydrocephalus due to idiopathic aqueductal stenosis

Two cases of parkinsonism after recurrent obstructive hydrocephalus due to idiopathic aqueductal stenosis are reported. In both patients an extrapyramidal syndrome was noted in the absence of contemporaneous evidence of hydrocephalus or shunt failure. One of the patients underwent a shunt operation, but showed no clinical improvement. However, both patients improved after the administration of dopaminergic therapy. The seven previously reported cases of this syndrome were reviewed and it is concluded that the prognosis of the parkinsonism is good, usually with total, or near total, resolution. It is recommended that if a patient with idiopathic aqueduct stenosis develops hydrocephalus or evidence of shunt malfunction in association with acute parkinsonism their shunt should be replaced. If there is no evidence of hydrocephalus or shunt malfunction they should initially be treated with domaminergic medication.

Nerve injury after posterior and direct lateral approaches for hip replacement. A clinical and electrophysiological study

Nerve injury is a rare complication of total hip replacement which may be related to the exposure used for the operation. The posterior approach is traditionally associated with injury to the sciatic nerve. We have compared the incidence of nerve injury after primary total hip replacement (THR) using either a posterior or a direct lateral approach. We studied 42 consecutive patients undergoing primary total hip replacement. The surgeons used a posterior (22 patients) or direct lateral (20 patients) approach in accordance with their normal practice. The obturator, femoral, posterior tibial and common peroneal nerves were assessed clinically and electrophysiologically by electromyography (EMG) and measurement of the velocity of nerve conduction before operation and at four weeks after. All patients were free from symptoms of nerve injury after operation but five lesions were identified in four patients by the electrophysiological studies; the obturator nerve was involved in two, the femoral in one, the common peroneal in one and the posterior tibial in one. All these injuries occurred using the lateral approach. Clinical assessment alone underestimates the incidence of nerve injury complicating THR. Our study does not confirm the association of nerve injury with the posterior approach which had been described previously.

Focal upper limb demyelinating neuropathy

Observations are presented on nine selected patients with chronic upper limb demyelinating neuropathy to illustrate the range of manifestations that may be observed. In three, the involvement was purely motor, in five, mixed motor and sensory and, in one, virtually purely sensory; in seven the symptoms were unilateral and in two bilateral. The presence of reduced nerve conduction velocity and conduction block and the response to treatment in seven of the cases indicate that they represented examples of chronic inflammatory demyelinating polyneuropathy (CIDP) with focal involvement. This was confirmed by nerve biopsy in two cases. The presentation in one patient was accompanied by forearm swelling initially suspected of being a tumour but shown to be due to muscle hypertrophy. This was probably the consequence of recurrent muscle cramps and fasciculation and possibly neuromyotonia. The patient with predominant sensory involvement restricted to the upper limbs demonstrates that sensory CIDP can present focally. In one patient with monomelic motor and sensory involvement, nerve biopsy showed multifocal areas of hypertrophic demyelinating neuropathy distally in the ulnar nerve without inflammatory infiltration. This patient failed to respond to therapy. Response in the others was satisfactory, although one patient with a monomelic motor neuropathy showed a severe deterioration after being given corticosteroids; he subsequently improved with intravenous human immunoglobulin therapy.

Plasma exchange in the treatment of Guillain-Barré syndrome: experience in a sub-regional referral centre

Plasma exchange became popular in the treatment of Guillain-Barré syndrome with the publication in 1985 of results by the Guillain-Barré Study Group. Since then we have treated 24 patients referred for plasma exchange. We have audited their outcome and compared this with the results of patients in the treatment arm of the USA Study. Our patients were of comparable age and clinical severity and had similar duration of illness before starting plasma exchange. Nine of our patients required ventilation for a median of 24 days. The median time to improve one clinical grade was 19 days which compared well with the Study Group results. We have shown that plasma exchange may be safely performed in a district general hospital in a setting appropriate to the patient's clinical condition. We concur with the central conclusion of the Study, that if treatment is started early in the disease, the patient's outcome is improved.

Mononeuritis multiplex and occipital infarction complicating giant cell arteritis

A 67-year-old lady with giant cell arteritis presented with a normal erythrocyte sedimentation rate (ESR) and developed occipital infarction and mononeuritis multiplex shortly after being started on high dose steroids.

Stretch and vibration reflexes of wrist flexor muscles in spasticity

The surface electromyographic (EMG) reflex responses of the voluntarily contracting flexor carpi radialis evoked by 'stretch' and by tendon vibration have been compared in patients with spasticity of the upper limb, arising from upper motor neuron lesions, and normal subjects. Reflex responses to 'stretch' comprised increases in EMG activity lasting up to 100 ms which were often divided into 'short' and 'long'-latency peaks. The short-latency responses of spastic patients were increased in size compared with those of normal subjects whereas later activity was commonly reduced or absent. In both groups vibration elicited short-latency, essentially phasic responses with activity falling back to or below the background level within 50 ms despite continuing stimulation. These initial reflex responses were exaggerated in the spastics as compared with the normals. In the relaxed state 'stretch' and vibration either failed to elicit reflex responses in normal subjects or reflexes were of small amplitude; in spastic patients both modes of stimulation regularly evoked well developed responses. These findings with 'stretch' and vibration, both of which forms of stimulation powerfully excite primary endings of muscle spindles, support the view that group Ia afferent-mediated reflex action is enhanced in spasticity. The observation that the normal long-latency responses evoked by stretch, which have been attributed to the action of spindle group II afferents (Matthews, 1984a) additionally excited with this stimulus, are depressed in many spastic patients is consistent with reduced group II effects. Observed abnormalities of stretch reflex behaviour did not readily explain the severity of accompanying spasticity of individual patients.

Brain stem auditory evoked potentials and blink reflexes in multiple sclerosis

Brain stem auditory evoked potentials (BAEP) and the blink reflex (BR) were recorded from 50 patients with a wide spectrum of multiple sclerosis, to determine whether the combination of the two tests of brain stem function would yield a higher rate of abnormality than each test performed alone. Sixty-four per cent of patients had a BAEP abnormality and fifty-two per cent had an abnormal BR, but when the results were combined, seventy-six per cent were abnormal. The blink reflex was abnormal in all patients with symptoms suggestive of trigemino-facial pathology.

An adult case of Andersen's disease--Type IV glycogenosis. A clinical, histochemical, ultrastructural and biochemical study

A middle-aged man presented with a thirty-year history of progressive, asymmetrical limb-girdle weakness. The muscle biopsy revealed a vacuolar myopathy. The vacuoles which did not disrupt the fibre outline, lay in a subsarcolemmal position. They were PAS-positive and the material was partially resistant to diastase digestion. Electron microscopy showed the vacuoles to contain free unbound glycogen with filamentous material. Leucocyte brancher enzyme activity was normal but the muscle activity was less than half the control value. Histochemical and ultrastructural characteristics of the storage material resemble the amylopectin polysaccharide deposits seen in childhood Type IV glycogenosis.

Facial nerve preservation during surgery for removal of acoustic nerve tumors

A series of 33 patients with 35 acoustic nerve tumors is reviewed. Tumor size was estimated from computerized tomography (CT) scans, and its influence on anatomical and functional preservation of the facial nerve was assessed. Six tumors (one invading the petrous bone, three medium and two large tumors) were not detected on CT scans. The translabyrinthine approach was used in seven instances (one small and six medium tumors) and the suboccipital transmeatal approach for 28 tumors (seven medium and 21 large tumors). Anatomical preservation of the facial nerve was achieved in 83% of operations for tumor removal, two of which were subtotal. A further two patients underwent subtotal removal, but the facial nerve was destroyed. Large tumors carried an increased risk of damage to the facial nerve, but even in this group the nerve was preserved anatomically intact in 70% of cases. Damage to the facial nerve occurred more frequently in patients with preoperative evidence of facial weakness; however, this factor did not appear to influence functional recovery of the facial nerve, provided that the nerve was intact at the end of the operation. A simple grading system for facial nerve function is described. Ony 76% of anatomically intact facial nerves showed any evidence of function 1 month after surgery. Postoperatively, facial function improved with time. At the latest review, 45% of these patients had normal facial function or mild facial weakness (Grades I and II).

Ventilatory failure in myasthenia gravis

This retrospective study over the decade 1969-1978 examines the precipitating factors and outcome in thirty-one patients with myasthenia gravis who developed ventilatory failure. An unusual example of chronic alveolar hypoventilation is discussed in detail. The most favourable outcome occurred in younger patients with a hyperplastic thymus, in contrast to a poorer outlook for older patients with an atrophic gland. Eleven patients died during the period of follow up: three deaths were unrelated to myasthenia but the remaining eight were attributed directly or indirectly to it. The mortality of 36% represents a marked improvement on a 70% mortality in a similar group of patients, reported from this hospital for the years 1960-1968.

Livedo reticularis and cerebro-vascular disease

Three cases are described in which extensive livedo reticularis was associated with premature cerebrovascular disease. The patients presented with transient cerebral ischaemic attacks and gradually developed permanent neurological damage with intellectual impairment. The value of detailed neuropsychological testing to identify bilateral cortical abnormalities is demonstrated. CAT scanning may reveal multifocal cerebral infarction. The nature of this condition is not understood.

Habituation of the orbicularis oculi reflex in dementia and dyskinetic states

The habituation index is a quantitative expression of the ability of the orbicularis oculi (blink reflex) to adapt to a series of electrical stimuli applied to the supraorbital region. This parameter has been studied in a group of normal control subjects, and the results compared with those in cases of idiopathic and drug-induced Parkinsonism, states of dementia, and dyskinesias such as Huntington's chorea and senile chorea. Patients with Huntington's chorea showed a tendency for the reflex to habituate readily in contrast to patients with dementia caused by cortical atrophy and those with Parkinson's disease. Younger patients with Huntington's chorea had indices within the normal range. It seems unlikely that this test will prove of value in the detection of clinically unaffected relatives. Where dementia was associated with a reversible intracranial lesion, the habituation index was studied before and after treatment. Failure of habituation in this condition appears to be due to the release of a primitive protective reflex.

Electrical study of jaw and orbicularis oculi reflexes after trigeminal nerve surgery

Trigeminal nerve ophthalmic and motor division function was assessed clinically and electrically in 32 patients who had undergone various surgical procedures for trigeminal neuralgia. Using known electrophysiological techniques, the orbicularis oculi and jaw reflexes were tested in all subjects. Abnormalities of the orbicularis oculi reflex were anticipated on the basis of ophthalmic division anaesthesia. However, jaw reflex abnormalities appeared in operated cases with no clinical or electromyographic evidence of masseter denervation. These results were unexpected, and imply that the proprioceptive fibres of the jaw reflex are mediated by a sensory and not a motor root as previously believed.

Laryngeal tetany: an unusual presentation of chronic renal failure

The presenting features and subsequent management of two adult patients with chronic renal failure complicated by laryngospasm are described. Possible mechanisms to explain this uncommon phenomenon are discussed but its rarity remains unexplained.

Sodium valproate in chorea

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