Saccades and multisaccadic gaze shifts are gated by different pontine omnipause neurons in head-fixed cats

 Pontine omnipause neurons (OPNs) have so far been considered as forming a homogeneous group of neurons whose tonic firing stops during the duration of saccades, when the head is immobilized. In cats, they pause for the total duration of gaze shifts, when the head is free to move. In the present study, carried out on alert cats with fixed heads, we present observations made during self-initiated saccades and during tracking of a moving target which show that the OPN population is not homogeneous. Of the 76 OPNs we identified, 39 were found to have characteristics similar to those of previously described neurons, ”saccade” (S-) OPNs: (1) the durations of their pauses were significantly correlated with the durations of saccades; (2) the discharge ceased shortly before saccade onset and resumed before saccade end; (3) visual responses to target motion were excitatory; and (4) during tracking, S-OPNs interrupted the discharge for the duration of saccades and resumed firing during perisaccadic ”drifts”. However, the characteristics of 37 neurons (”complex” (C-) OPNs) were different: (1) the pause duration was not correlated with the duration of self-initiated saccades; (2) time lead of pause onsets relative to saccades was, on average, longer than in the group of S-OPNs, and firing resumed after the saccade end; (3) visual target motion suppressed tonic discharges; and (4) during tracking, firing was interrupted for the total duration of gaze shifts, including not only saccades but also perisaccadic ”drifts”. We conclude that cat OPNs can be subdivided into two main groups. The first comprises neurons whose firing patterns are compatible with gating individual saccades (”saccade” OPNs). The second group consists of ”complex” OPNs whose firing characteristics are appropriate to gate total gaze displacements rather than individual saccades. The function of these neurons may be to disinhibit pontobulbar circuits participating in the generation of saccade sequences and associated perisaccadic drifts. Received: 20 January 1998 / Accepted: 22 October 1998     

"Hemicrania continua": The first bilateral case?

The patient reported had had a continuous headache involving the whole skull for 7 years. Many drugs had failed to relieve the pain, but with indomethacin the headache completely disappeared within 3 days. Nine months later the treatment was discontinued without any relapse. This variety of headache, not previously reported, was quite similar to the "hemicrania continua" except for its localization.     

Synovial cysts of unusual localization. 2 cases and review of the literature

Two patients with true synovial cysts in atypical sites (internal compartment of knee and inguinal hollow) were investigated by radioarthrography, ultrasound and computed tomography imaging. The cyst in the hip region originated from a dilated serous bursa of the iliopsoas muscle that did not communicate or was no longer in communication with the joint. In contrast, the cyst of the knee appeared to be a lateral synovial capsule hernia. Positive diagnosis in both cases was dependent on combined ultrasound-CT scan imaging, this eliminating a tumor (sarcoma) of soft tissues. However, affirmation of the synovial origin (mesothelial covering of the wall) of the lesion was obtained by histology only, this allowing differentiation from a "capsular" (fibrous wall) cyst, which probably provokes similar ultrasound and CT scan images.     

Hospital-at-Home Expands Hospital Capacity During COVID-19 Pandemic

A Coronavirus Disease 2019 (COVID-19)–specific Hospital-at-Home was implemented in a 400-bed tertiary hospital in Barcelona, Spain. Senior or immune-compromised physicians oversaw patient care. The alternative to inpatient care more than doubled beds available for hospitalization and decreased the risk of transmission among patients and health care professionals. Mild cases from either the emergency department or after hospital discharge were deemed suitable for admission to the Hospital-at-Home. More than half of all patients had pneumonia. Standardized protocols and management criteria were provided. Only 6% of cases required referral for inpatient hospitalization. These results are promising and may provide valuable insight for centers undertaking Hospital-at-Home initiatives or in the case of new COVID-19 outbreaks.     

Rural and urban variation in psychological distress among adults: results of the 2014–2015 Eastern Townships Population Health Survey (ETPHS)

ObjectiveA growing number of people live in urban areas. Urbanization has been associated with an increased prevalence of mental disorders, but which mechanisms cause this increase is unknown. Psychological distress is a good indicator of mental health. This study sought to examine the relationship between urbanization and distress among adults in the Eastern Townships (southern region of Quebec, Canada).MethodIn the 2014–2015 Eastern Townships Population Health Survey (N = 10,687 adults living in one of the 96 Eastern Townships communities), distress was measured with the K6 distress scale (≥ 7). Urbanization was estimated by the residential density of the community treated in quintiles. Logistic regression analyses were carried out with adjustments for individual and environmental characteristics.ResultsWomen, young people aged 18–24, single parents, those without diplomas, those without a job, those with < $20,000 in income, adults with two or more chronic physical illnesses, adults with bad perceived health, or those living in disadvantaged neighbourhoods exhibited more distress. The unadjusted estimate between density and distress is only significant for the fifth quintile when compared with the first quintile (OR 1.23; 95% CI: 1.06–1.42). The relationship is practically the same after controlling for individual characteristics but decreases considerably after controlling for environmental characteristics (lack of trees, social deprivation, intersection density, vegetation index, and land use mix).ConclusionThis study was the first to examine an association between urbanization and distress by considering individual and environmental characteristics. The latter seem to explain the relationship between these concepts.     

Patient-specific mechanical properties of a flexible multi-body model of the scoliotic spine

The flexibility of the scoliotic spine is an important biomechanical parameter to take into account in the planning of surgical instrumentation. The objective of the paper was to develop a method to characterisein vivo the mechanical properties of the scoliotic spine using a flexible multi-body model. Vertebrae were represented as rigid bodies, and intervertebral elements were defined at every level using a spherical joint and three torsion springs. The initial mechanical properties of motion segments were defined fromin vitro experimental data reported in the literature. They were adjusted using an optimisation algorithm to reduce the discrepancy between the simulated and the measured Ferguson angles in lateral bending of three spine segments (major or compensatory left thoracic, right thoracic and left lumbar scoliosis curves). The flexural rigidity of the spine segments was defined in three categories (flexible, nominal, rigid) according to the estimated mechanical factors (α). This approach was applied with ten scoliotic patients under-going spinal correction. Personalisation of the model resulted in an increase of the initial flexural rigidity for seven of the ten lumbar segments (1.38≤α≤10.0) and four of the ten right thoracic segments (1.74≤α≤5.18). The adjustment of the mechanical parameters based on the lateral bending tests improved the model's ability to predict the spine shape change described by the Ferguson angles by up to 50%. The largest differences after personalisation were for the left lumbar segments in left bending (4⁰±3⁰). Thein vivo identification of the mechanical properties of the scoliotic spine will improve the ability of biomechanical models adequately to predict the surgical correction, which should help clinicians in the planning of surgical instrumentation manoeuvres.     

Results and indications of lateral ileostomy functionally terminated in colorectal surgery

Loop ileostomy (LI) ensures fecal diversion to protect an anastomosis or anatomic colorectal or ano-perineal damage. The aim of this retrospective study was to evaluate loop ileostomy morbidity in emergency and planned colorectal surgery. PATIENTS AND METHODS: From 1991 to 1996, 145 loop ileostomies were performed in 139 patients, 77 men and 62 women with a mean age of 48.7 years (15-82). The etiology was a rectal tumor (cancer or large villous tumor n = 47), inflammatory bowel disease (n = 47, ulcerative colitis = 37 and Crohn's disease = 10) Familial Adenomatous Polyposis (n = 13) and other diseases (n = 32). 80% LI (n = 116) protected ileo-anal anastomoses (n = 46) colo-anal anastomoses (n = 45, 26 with colonic pouch), ileo-rectal anastomoses (n = 11) and other anastomoses (n = 15). 20% LI (n = 29) dysfunctional ano-perineal lesions (n = 8), anastomosis leak (n = 4) or distal bowel without intestinal resection (n = 17). RESULTS: 7 deaths were not stoma-related. 91% LI were closed after a mean diversion time of 3.6 months. LI closure was performed by a parastomal (n = 128) or laparotomy procedure (n = 4). Morbidity during LI diversion was observed in 24 patients (16.5%) 12 of whom (8.3%) were operated for small bowel obstruction (n = 6; 4.2%) stoma revision (n = 5; 3.5%) and prolapse (n = 1; 0.7%). 2 patients had peristomal skin excoriations, and 5 patients required readmission for dehydration due to high LI output. Morbidity after LI closure was observed in 12 patients (8.6%) 5 of whom were operated for anastomotic leak (n = 4) or small bowel obstruction (n = 1). Low morbidity and defunctioning efficiency confirm the indications for LI. LI is our first-line stoma in planned or emergency colorectal surgery.     

EEG and cardiac activation during periodic leg movements in sleep: support for a hierarchy of arousal responses

OBJECTIVE: To investigate other physiologic changes that occur with periodic leg movements during sleep (PLMS) that might be considered to be more sensitive indices of sleep fragmentation. BACKGROUND: Although PLMS are associated with recurrent microarousals (MA), the frequency of PLMS with MA does not correlate with objective daytime sleepiness. It is postulated that the lack of correlation results from the low sensitivity of the standard criteria used to score MA. METHODS: Ten drug-free patients with a polygraphic and clinical diagnosis of restless legs syndrome (RLS) and PLMS were examined. The EEG correlates of PLMS were analyzed by visual scoring and spectral analysis during PLMS that ended in a visible microarousal (PLMS with MA) or not (PLMS without MA). The R-R interval in the EKG signal was also examined. RESULTS: A total of 34% of PLMS were associated with MA lasting >3 seconds, and 3% of PLMS were associated with MA lasting <3 seconds. Although PLMS with MA were associated with an increase in alpha activity, for PLMS without MA a significant increase in delta and theta activity was present. Both types of PLMS induced a shortening of the R-R interval; this was particularly more marked for PLMS with MA. CONCLUSIONS: First, visual scoring of MA that include a duration of less than 3 seconds has little effect on the detection of PLMS with MA. Second, EEG activation and tachycardia are present during both types of PLMS. Third, a hierarchy in the arousal response is present-going from autonomic activation to bursts of delta activity to alpha activity to a full awakening.     

Sequential changes in the synaptic structural profile following long-term potentiation in the rat dentate gyrus: I. The intermediate maintenance phase

Changes in synaptic structure have been reported following the induction of long-term potentiation (LTP). The structure of synapses during the intermediate maintenance of LTP has yet to be fully characterized in chronically implanted freely moving animals. The present study examined synapses in the middle third of the molecular layer (MML) of the rat dentate gyrus following repeated high frequency tetanization of the perforant path. Synapses from both 1) the ipsilateral inner third of the dentate molecular layer (IML), which was not directly stimulated during the induction of LTP, as well as 2) implanted, nonstimulated animals, served as controls. LTP was induced over a 4-h period, and the animals were sacrificed 24 h after the final stimulation of the LTP group. Ultrastructural quantification included the total number of synapses, synaptic curvature, the presence of synaptic perforations, and the maximum length of the synaptic contact. Although LTP was not associated with an overall increase in synaptic number, there was a significant increase in the proportion of presynaptically concave-shaped synapses. Further, the concave synapses in the LTP tissue were found to be significantly smaller than control concave synapses. There was also a significant increase in the number of perforated concave synapses which exceeded the overall increase in concave synapses, and occurred despite the lack of a general increase in perforated synapses. It was concluded that this specific structural profile, observed at 24 h postinduction, may help support the potentiated response observed at this stage of LTP maintenance.