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PubMed1993

Neuroanatomical substrate for the dorsal light response. I. Differential afferent connections of the lateral lobe of the valvula cerebelli in goldfish (Carassius auratus).

The afferent connections of the lateral lobe of the valvula cerebelli in goldfish were investigated by retrograde labeling with horseradish peroxidase (HRP). Retrogradely labeled neurons were observed ipsilaterally in the lateral nucleus of the valvula and contralaterally in the inferior olivary nucleus after HRP injection into all parts of the lateral valvula. The valvulopetal projections from these nuclei were topographically arranged. After HRP injection confined to the rostral half of the lateral valvula, labeled neurons were also found ipsilaterally in the octavolateral and trigeminal cell groups: the eminentia granularis, the medial nucleus of the octavolateralis column, and the isthmic primary sensory trigeminal nucleus. HRP injection confined to the caudal half of the lateral valvula resulted in retrograde labeling of the following vision-related cell groups; the central pretectal nucleus, nucleus paracommissuralis, and the nucleus isthmi. However, the octavolateral and trigeminal cell groups did not project to the caudal half of the lateral valvula. These data provide insight into central nervous integration of visual and vestibular information, and help reveal the mechanism of the dorsal light response (DLR). Bilateral lesions of either the valvula cerebelli or pretectal area completely abolish this visually-guided response, but lesions of the optic tectum have no such effect. The pretectal nuclei (central pretectal nucleus, nucleus paracommissuralis) project to the lateral valvula directly, not via the optic tectum. These direct projections from the pretectal accessory optic nuclei to the lateral valvula may control the DLR. On the other hand, the lateral valvula receives vestibular and lateral line inputs indirectly, via the eminentia granularis and the medial nucleus of the octavolateralis column, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Afferent Pathways↗
PubMed1982

Lateral septum-medial hypothalamic connections: an electrophysiological study in the rat.

Participation of both the lateral septum and the medial hypothalamus in similar behavioral and homeostatic functions, combined with anatomical data indicating a modest descending lateral septum projection to medial hypothalamic areas, prompted an investigation of the electrophysiology of lateral septum--medial hypothalamic connections in pentobarbital-anesthetized male Sprague-Dawley rats. Field potentials evoked by lateral septum stimulation were prominent within the hypothalamic ventromedial nucleus: their distribution closely overlapped with amygdala-evoked field potentials. Lateral septum stimulation evoked orthodromic responses from 67% of 800 medial hypothalamic and preoptic neurons (55.5% excitatory, latency 17.5 +/- 0.5 ms; 11.5% inhibitory, latency 19.1 +/- 1.4 ms), including 15 of 31 tuberoinfundibular neurons activated antidromically from the median eminence, 37.4% of cells responded orthodromically to both lateral septum and amygdala stimulation, whereas only 5.8% of cells demonstrated orthodromic responses to both lateral septum and midbrain periaqueductal gray stimulation. These observations suggest that lateral septum neurons influence the excitability of many medial preoptic and hypothalamic neurons, and indicate a convergence of lateral septum and amygdala influences onto 37% of medial hypothalamic cells. In the rat, the lateral septum's influence on adenohypophyseal hormone secretion appears to be mediated indirectly, i.e. through monosynaptic connections with medial hypothalamic tuberoinfundibular neurons.

Amygdala↗
PubMed1996

Projections of the medial and lateral prefrontal cortices to the amygdala: a Phaseolus vulgaris leucoagglutinin study in the rat.

The projections of different subfields of the medial and lateral prefrontal cortices to the amygdala were studied in the rat using the sensitive Phaseolus vulgaris leucoagglutinin anterograde tract tracing technique. Injections into the infralimbic cortex produced anterograde labeling in the lateral capsular subdivision of the central nucleus, superficial (corticomedial) amygdaloid nuclei, lateral and accessory basal nuclei, and the anterior amygdaloid area. Injections into the caudal portion of the infralimbic cortex produced additional labeling in the intermediate subdivision of the central nucleus. The prelimbic cortex had projections to the medial portion of the magnocellular basal nucleus and adjacent portions of the lateral nucleus and lateral capsular subdivision of the central nucleus. The medial precentral cortex had projections to the rostromedial part of the magnocellular basal nucleus and adjacent portions of the lateral capsular subdivision of the central nucleus. Injections into the lateral orbital and ventral agranular insular cortices produced labeled fibers in the rostral part of the superficial amygdala, lateral capsular subdivision of the central nucleus, and the lateral and accessory basal nuclei. The dorsal agranular insular area had projections to several different subdivisions of the central nucleus as well as to the rostrolateral magnocellular basal nucleus; the latter projections were complementary to those originating in the prelimbic area. The present study indicates that each portion of the prefrontal cortex has a distinctive projection to the amygdala. The ventral areas of the lateral and medial prefrontal cortices, which receive olfactory projections, are the only prefrontal cortical areas with projections to the olfactory-related superficial amygdaloid nuclei. The more dorsally situated prefrontal areas, the dorsal agranular insular area and prelimbic cortex, have complementary projections to the basal nucleus, suggesting that they modulate separate prefrontal cortico-striatal-pallid circuits. The specificity of prefrontal cortico-amygdaloid projections is indicative of their involvement in discrete functions.

Amygdala↗
PubMed2006

Alpha2-adrenergic activation in the lateral parabrachial nucleus induces NaCl intake under conditions of systemic hyperosmolarity.

The inhibition of sodium intake by increased plasma osmolarity may depend on inhibitory mechanisms present in the lateral parabrachial nucleus. Activation of alpha(2)-adrenergic receptors in the lateral parabrachial nucleus is suggested to deactivate inhibitory mechanisms present in this area increasing fluid depletion-induced 0.3 M NaCl intake. Considering the possibility that lateral parabrachial nucleus inhibitory mechanisms are activated and restrain sodium intake in animals with increased plasma osmolarity, in the present study we investigated the effects on water and 0.3 M NaCl intake produced by the activation of alpha(2)-adrenergic receptors in the lateral parabrachial nucleus in rats with increased plasma osmolarity. Male Holtzman rats with stainless steel cannulas implanted bilaterally into the lateral parabrachial nucleus were used. One hour after intragastric 2 M NaCl load (2 ml), bilateral injections of moxonidine (alpha(2)-adrenergic/imidazoline receptor agonist, 0.5 nmol/0.2 microl, n=10) into the lateral parabrachial nucleus induced a strong ingestion of 0.3 M NaCl intake (19.1+/-5.5 ml/2 h vs. vehicle: 1.8+/-0.6 ml/2 h), without changing water intake (15.8+/-3.0 ml/2 h vs. vehicle: 9.3+/-2.0 ml/2 h). However, moxonidine into the lateral parabrachial nucleus in satiated rats not treated with 2 M NaCl produced no change on 0.3 M NaCl intake. The pre-treatment with RX 821002 (alpha(2)-adrenergic receptor antagonist, 20 nmol/0.2 microl) into the lateral parabrachial nucleus almost abolished the effects of moxonidine on 0.3 M NaCl intake (4.7+/-3.4 ml/2 h). The present results suggest that alpha(2)-adrenergic receptor activation in the lateral parabrachial nucleus blocks inhibitory mechanisms, thereby allowing ingestion of hypertonic NaCl under conditions of extracellular hyperosmolarity. We suggest that during cell dehydration, circuits subserving sodium appetite are activated, but at the same time strongly inhibited through the lateral parabrachial nucleus.

Adrenergic alpha-Antagonists↗
PubMed2003

The consequences of lateral release in total knee replacement: a review of over 1000 knees with follow up between 5 and 11 years.

BACKGROUND: The relationship between lateral release in total knee arthroplasty and subsequent patello-femoral problems is contentious. Variable rates of instability, patella fracture and other complications have been demonstrated after lateral release. Significant measures have been taken by some surgeons to avoid a lateral release. We wished to determine whether lateral release was detrimental or beneficial in terms of mid- to long- term patellofemoral problems. METHODS: We examined 1071 total knee arthroplasties with a follow-up of 5 to 11 years to determine the longer-term consequences of lateral release. Lateral release was performed as clinically indicated after a 'no thumbs' assessment in 51% of cases. The knees requiring a lateral release had lower pre-operative Hospital for Special Surgery (HSS) scores and demonstrated a greater improvement in post-operative HSS scores. RESULTS: The difference in HSS scores, between the groups, was significantly less post-operatively than prior to surgery. Overall, we had a high incidence of lateral release (51%), but low fracture rate (1.2%), and very low instability rate (0.6%). Only three surgeries were required for patello-femoral problems. CONCLUSION: This study suggests that any negative consequences of lateral release are minimal and we recommend lateral release continue to be performed as clinically indicated.

Aged↗
PubMed1991

Visuotopic organization of the lateral suprasylvian area and of an adjacent area of the ectosylvian gyrus of cat cortex: a physiological and connectional study.

We have explored the visuotopic organization of the territory surrounding the middle suprasylvian sulcus (MSS) of cat cerebral cortex by electrophysiological mapping, and by tracing the topography of its cortical and subcortical connections using wheatgerm-agglutinin horseradish peroxidase (WGA-HRP). Observations from the two approaches were concordant, and confirmed the presence of two separate visual areas in the MSS that approximate, but do not exactly correspond, to the location and internal organization of the posterior medial and posterior lateral lateral suprasylvian (PMLS, PLLS) areas of Palmer et al. (1978). We define as part of the lateral suprasylvian (LS) area the territory on the medial bank and caudal end of the lateral bank of the MSS that receives a topographically organized projection from the region of area 17 representing the lower visual quadrant. This territory is connected with other structures that are themselves striate-recipient (cortical areas 18 and 19, and the lateral division of the lateral posterior (LPl) nucleus), and with a variety of nuclei that receive direct retinal input, such as the C-laminae of the LGd, the medial interlaminar nucleus (MIN), and the superficial layers of the superior colliculus (SC). Its connections with the LPl, LGd, MIN, and SC correspond topographically with the input from area 17. Revised maps of area LS were produced from the physiological and connectional data: its rostral border is formed by a representation of lower visual elevations with the horizontal meridian represented caudally, and its lateral border is formed by the vertical meridian; area LS shares a representation of the center of gaze with the visual area of the lateral bank at its caudal end. The adjacent lateral bank area has larger receptive fields than area LS, and very different connectivity. It receives no input from area 17 and little input from striate-recipient structures, including area LS, but instead is connected to more remote extrastriate visual areas, such as the anterior ectosylvian visual (AEV) area in insular cortex, and to zones of the thalamus in receipt of tectal input (LPm and the lateromedial-suprageniculate nuclear complex). According to both mapping approaches, the lateral bank area contains representations of both the upper and lower visual quadrants but a rather limited degree of visuotopic order. We refer to it as the posterior ectosylvian visual (PEV) area, because it appears to be functionally and connectionally dissociated from area LS, but is possibly a functional antecedent of area AEV.

Animals↗
PubMed1976

Assessment of velar and lateral wall movement by oral telescope and radiographic examination in patients with velopharyngeal inadequacy and in normal subjects.

Thirty-one patients referred to the Craniofacial Anomalies Clinic for speech evaluation were evaluated by endoscopy and cineradiographic examination (lateral and submentovertical projection). Movement of the velar and lateral walls was examined by both procedures in order to determine the accuracy of the endoscopy in assessing velopharyngeal movement. Cineradiography confirmed endoscopic observation in a large percentage of patients. In a second study, lateral wall motion was assessed in 20 cleft palate patients with repaired hard and soft palate but with velopharyngeal inadequacy. Four categories of closure defined in a previous study on normal subjects were used to classify lateral wall movement in the cleft palate patients. Mesial lateral motion past the sides of the velum during phonation occurred less frequently in patients with velopharyngeal inadequacy than in persons with normal strucutres. The absence of lateral wall motion was observed more often in the cleft palate patients, although in over half of these patients the lateral walls moved mesially and filled Rosenmuller's fossa (lateral recesses). Degree of lateral wall movement, which varies among cleft palate patients, should be estimated before construction of a prosthesis or pharyngeal flap in order to determine whether occlusion of the lateral gutters will occur during phonation.

Adolescent↗
PubMedDate not supplied

Radiographic knee dimensions in discoid lateral meniscus: comparison with normal control.

We reviewed the knee radiographs of 68 cases of arthroscopically proven discoid lateral meniscus, including 42 cases of complete type and 26 cases of incomplete type discoid lateral meniscus. Knee radiographs of 70 cases that had no arthroscopic evidence of pathology of the meniscus were used as controls. We excluded patients who had significant trauma history and who were under 16 years of age or over 60 years to avoid measuring radiographs of skeletally immature or degenerative knees. The absolute values and relative normalized values of specific knee dimensions, such as a squared-off appearance of the lateral femoral condyle, widened femorotibial joint space, cupping of the lateral tibial plateau, obliquity of the lateral tibial plateau articular surface, high fibular head, and hypoplasia of the lateral intercondylar spine, were compared between the patients with discoid lateral meniscus and the normal controls. Among those dimensions, high fibular head and widened lateral tibiofemoral joint space showed statistically significant differences between the discoid lateral meniscus group and normal control group. We suggest that these findings would be useful in screening lateral discoid meniscus on plain radiography.

Adolescent↗
PubMedDate not supplied

Single-strand reconstruction of the lateral ulnar collateral ligament restores varus and posterolateral rotatory stability of the elbow.

Because of a lack of biomechanical studies of lateral elbow ligament reconstruction in the literature, the initial stability afforded by 3 different techniques of lateral ulnar collateral ligament reconstruction was evaluated in 8 cadaveric elbows. The arm was mounted in a testing apparatus, and passive flexion was performed with the arm in varus and valgus orientations. A pivot shift test was performed with the arm in the vertical orientation. An electromagnetic tracking device was used to quantify motion pathways. After intact testing, each specimen underwent sectioning of the radial collateral and lateral ulnar collateral ligaments from the lateral epicondyle. Reconstruction of the lateral ulnar collateral ligament was performed in a randomized sequence, consisting of proximal single-strand, distal single-strand, and double-strand tendon grafts. Division of the radial collateral and lateral ulnar collateral ligaments from the lateral epicondyle caused a significant decrease in rotational stability when the pivot shift test was being performed (P <.0001). Varus-valgus stability also decreased after transection of the radial collateral and lateral ulnar collateral ligaments (P <.0001). Reconstruction of the lateral ulnar collateral ligament restored elbow stability to that of the intact state. There was no significant difference in stability between the single- and double-strand repair techniques (P >.05). This study demonstrates that both single- and double-strand reconstructions restore varus and posterolateral elbow stability and may be considered appropriate reconstructive procedures in patients with symptomatic insufficiency of the lateral ligaments of the elbow.

Aged↗
PubMed2001

Women's exposure to early and later life socioeconomic disadvantage and coronary heart disease risk: the Stockholm Female Coronary Risk Study.

BACKGROUND: Measures of low socioeconomic position have been associated with increased risk for coronary heart disease (CHD) among women. A more complete understanding of this association is gained when socioeconomic position is conceptualized from a life course perspective where socioeconomic position is measured both in early and later life. We examined various life course socioeconomic indicators in relation to CHD risk among women. METHODS: The Stockholm Female Coronary Risk Study is a population-based case-control study, in which 292 women with CHD aged < or =65 years and 292 age-matched controls were investigated using a wide range of socioeconomic, behavioural, psychosocial and physiological risk factors. Socioeconomic disadvantage in early life (large family size in childhood, being born last, low education), and in later life (housewife or blue-collar occupation at labour force entry, blue-collar occupation at examination, economic hardships prior to examination) was assessed. RESULTS: Exposure to early (OR = 2.65, 95% CI : 1.12-6.54) or later (OR = 5.38, 95% CI : 2.01-11.43) life socioeconomic disadvantage was associated with increased CHD risk as compared to not being exposed. After simultaneous adjustment for marital status and traditional CHD risk factors, early and later socioeconomic disadvantage, exposure to three instances of socioeconomic disadvantage in early life was associated with an increased CHD risk of 2.48 (95% CI : 0.90-6.83) as compared to not being exposed to any disadvantage. The corresponding adjusted risk associated with exposure to later life disadvantage was 3.22 (95% CI : 1.02-10.53). Further analyses did not show statistical evidence of interaction effects between early and later life exposures (P = 0.12), although being exposed to both resulted in a 4.2-fold (95% CI : 1.4-12.1) increased CHD risk. Exposure to cumulative socioeconomic disadvantage (combining both early and later life), across all stages in the life course showed strong, graded associations with CHD risk after adjusting for traditional CHD risk factors. Stratification of cumulative disadvantage by body height showed that exposure to more than three periods of cumulative socioeconomic disadvantage had a 1.7- (95% CI : 0.9-3.2) and 1.9- (95% CI : 1.0-7.7) fold increased CHD risk for taller and shorter women, respectively. The combination of both short stature and more than two periods of cumulative socioeconomic disadvantage resulted in a 4.4-fold (95% CI : 1.7-9.3) increased CHD risk. CONCLUSIONS: Both early and later exposure to socioeconomic disadvantage were associated with increased CHD risk in women. Later life exposure seems to be more harmful for women's cardiovascular health than early life exposure to socioeconomic disadvantage. However, being exposed to socioeconomic disadvantage in both early and later life magnified the risk for CHD in women. Cumulative exposure to socioeconomic disadvantage resulted in greater likelihood of CHD risk, even among women who were above median height. In terms of better understanding health inequalities among women, measures of socioeconomic disadvantage over the life course are both conceptually and empirically superior to using socioeconomic indicators from one point in time.

Adult↗
PubMed1999

The lateral column lengthening and medial column stabilization procedures.

The results of medial column stabilization, lateral column lengthening, and combined medial and lateral procedures were reviewed in the treatment of adult acquired flatfoot secondary to posterior tibialis tendon insufficiency. All bony procedures were accompanied by transfer of the flexor digitorum longus tendon to the medial cuneiform or stump of the posterior tibialis tendon and tendoachilles lengthening or gastrocnemius recession. Medial column fusion was performed for naviculocuneiform and cuneiform first metatarsal sag; lateral column lengthening was performed for calcaneovalgus deformity with a flat pitch angle; and combined procedures were performed for complex combined deformities. At 1 to 4 year followup of 65 feet, 88% of the feet that had lateral column lengthening, 80% that had medial column stabilization, and 88% of the feet that had medial and lateral procedures had a decrease in pain or were pain free. The lateral talar first metatarsal angle improved by 16 degrees in the patients in the lateral column lengthening group, 20 degrees in the patients in the medial column stabilization group, and 24 degrees in the patients in the combined medial and lateral procedures group. The anteroposterior talonavicular coverage angle improved by 14 degrees in the patients in the lateral column lengthening group, 10 degrees in the patients in the medial column stabilization group, and 14 degrees in the patients in the combined medial and lateral procedures group. These techniques effectively correct deformity without disrupting the essential joints of the hindfoot and midfoot.

Achilles Tendon↗
PubMed1997

Adequacy and efficacy of lateral cervical spine radiography in alert, high-risk blunt trauma patient.

OBJECTIVE: The purpose of this study was to determine the adequacy and accuracy of lateral cervical spine radiographs in the initial evaluation of alert, high-risk trauma patients evaluated at a Level I trauma center. METHODS: Data were obtained retrospectively through review of trauma service admissions from January 1, 1994, to July 31, 1995. Included were all patients triaged to a trauma response team with age > 15 years, Glasgow Coma Scale score > 13, and blunt mechanism of injury. Lateral cervical spine radiograms were obtained routinely before secondary survey and were reviewed for technical adequacy (all seven cervical vertebrae, C7/T1 interspace). The presence of cervical symptoms (pain, tenderness, neurologic deficits) was recorded. Sensitivity and specificity were calculated for lateral cervical spine radiography and cervical symptoms in predicting the presence of cervical spine injury. Bayesian analysis, which allows for the current probability of occurrence to be factored by previously reported probabilities of occurrence, was used to determine the negative predictive probability of lateral cervical spine radiography and absence of cervical symptoms to predict the absence of injury to the cervical spine. RESULTS: Three hundred fifty-three patients received lateral cervical spine radiograms, of which 223 (63%) were determined to be adequate for interpretation. Cervical symptoms were present in 77 patients (20%). Only 32 (42%) of this group's lateral cervical spine radiograms were adequate. Nine patients (2.4%) had acutely fractured cervical vertebrae or ligamentous disruption. Lateral cervical spine radiography showed the injury in only six of these patients. The sensitivity, specificity, and negative predictive probability for lateral cervical spine radiography were 67, 58, and 1.4%, respectively, and for absence of cervical symptoms, 89, 81, and 0.32%, respectively. CONCLUSION: The higher accuracy and lower negative predictive probability make the absence of cervical symptoms in the alert, high-risk, blunt trauma patient a better screening test than lateral cervical spine radiography. We suggest that lateral cervical spine radiography is not needed in the initial evaluation of alert patients who have sustained blunt trauma.

Adult↗
PubMed1984

Selective alteration of palpebral fissure form by lateral canthopexy.

A method is described for altering the shape and position of the palpebral fissure at the lateral canthus. Three steps are essential to alter shape and position. They are (1) identification of a lateral canthal soft-tissue mass consisting of periosteum, lateral canthal ligament, and orbicularis muscle, (2) extensive subperiosteal soft-tissue mobilization of the lateral canthal soft-tissue mass (LCSTM) from a point just superior to the zygomaticofrontal suture and inferiorly along the infraorbital rim to a point corresponding with a vertical line drawn from the pupil downward, and (3) cutting of all soft tissue, including orbicularis muscle from dermis to bone and from bone to conjunctiva, from the lateral canthal soft-tissue mass medially to a point equal to a vertical line drawn from the pupil downward. After tension-free shifting laterally and superiorly has been accomplished, the lateral canthal soft-tissue mass is fixed into bone with minimal overcorrection. If there is still soft-tissue skin resistance, then overcorrection is desirable. The most difficult judgments in the procedure are the amount of superior and lateral tension to be placed on the palpebral fissure. As an aid in these judgments, the lateral-most extent of the palpebral fissure should be approximately 3 mm above the medial canthus horizontally and 3 to 4 mm medial to the medial-most portion of the lateral orbital rim. If overcorrection occurs, it can be released relatively simply.

Cephalometry↗
PubMed1998

The reliability of the lateral radiograph in determination of the optimal transarticular C1-C2 screw length.

STUDY DESIGN: This study assessed the value of using lateral radiographs in evaluating the optimal screw length in transarticular C1-C2 screw fixation. OBJECTIVES: To assess the reliability of the lateral radiograph in determining the optimal transarticular C1-C2 screw length. SUMMARY OF BACKGROUND DATA: Transarticular C1-C2 screw placement is usually performed using anatomic landmarks and fluoroscopy. A lateral fluoroscopic image is valuable when directing screws in the sagittal plane, but its exact role in determining screw length has not been investigated. METHODS: Eight cervical spine specimens were used in this study. Screw placements were performed in each specimen, fixed in the exact lateral position and under direct visualization. After each placement, a lateral radiograph was taken. The odontoid process was divided into three equal portions. Another portion anterior to the odontoid process was called the anterior tubercle region. The number of screw tips appearing in each portion on the radiograph was then recorded for each placement. In addition, 30 C1 specimens were measured to evaluate the anterior part of C1. RESULTS: The results showed that 12.5% of the screws placed 2 mm short of reaching the ventral cortex and 0 mm overpenetrating the ventral cortex of the lateral mass of C1 projected in the radiograph on the anterior tubercle region, 37.5% on the anterior region of the odontoid process, and 50% on the middle region of the odontoid process. Twenty-five percent of the screws that were placed to overpenetrate, by 2 or 4 mm, the ventral cortex of the lateral mass of C1 were projected on the anterior tubercle region in the radiograph, and 50% and 62.5% were projected on the anterior region of the odontoid process, respectively. The mean vertical distance between the anteriormost point of the anterior tubercle of the anterior ring and the middle of the ventral cortex of the lateral in all specimens was 5.6 +/- 1 mm, and the mean transverse angle of the anterior ring relative to the frontal plane was 21.1 +/- 3.5 degrees. CONCLUSIONS: This results in this study indicate that a lateral radiograph may not be reliable in determining the optimal screw length, although it is valuable in directing accurate screw angle in the sagittal plane. Preoperative computed tomographic evaluation of the C1-C2 region may be helpful in estimating the location of the screw tip on the lateral radiograph during surgery.

Adult↗
PubMed2005

Biomechanical comparison of transarticular facet screws to lateral mass plates in two-level instrumentations of the cervical spine.

STUDY DESIGN: In vitro biomechanical comparison of transarticular facet screws to lateral mass plates in two level instrumentations of the cervical spine. OBJECTIVE: Lateral mass plates are costly, and screw placement is difficult. Facet screws have never been tested as an alternative in the cervical spine. This biomechanical study compared cervical transarticular facet screws to lateral mass plates in two-level instrumentations of human cadaveric cervical spines. SUMMARY OF BACKGROUND DATA: Translaminar facet screws have been shown to have similar biomechanical performance to pedicle screw fixation in the lumbar spine, especially in flexion. They have proven to be fast, safe, and effective, with authors reporting 94% to 100% fusion rates in single-level lumbar fusions. However, a biomechanical comparison of transarticular facet screws to lateral mass plates in cervical spine instrumentations has not been reported. METHODS: Thirteen human cadaveric cervical motion segments (C2-C4, C5-C7) were tested before and after instrumentation, with either transarticular facet screws or lateral mass plates, in flexion, extension, lateral bending, and torsion. Specimens were subjected to six cycles under a load of 2 Nm. RESULTS: Both fixation systems significantly reduced range of motion (ROM) and increased stiffness compared with the intact state in flexion, extension, lateral bending, and torsion. There were also no significant differences between the facet screws and plates in any of the four directions. To compare the two systems, ROM of each was analyzed relative to the uninstrumented state. Flexion was 0.26 (or 26% of the intact state) for the transarticular facet screws versus 0.20 for the lateral mass plates (P = 0.34), extension was 0.10 versus 0.07 (P = 0.43), lateral bending was 0.17 versus 0.15 (P = 0.52), and torque was 0.25 versus 0.38 (P = 0.12). Load to failure testing failed to indicate any differences between the two methods of fixation because all the specimens failed elsewhere. CONCLUSION: This study proves that transarticular facet screws and lateral mass plates are equivalent in two-level instrumentations of the cervical spine. This is the first biomechanical study to test transarticular facet screws in this context.

Aged↗
PubMed2006

The feasibility of inserting atlas lateral mass screws via the posterior arch.

STUDY DESIGN: A total of 709 skeletally mature atlas specimens were obtained from the Hamann Todd Collection at the Cleveland Museum of Natural History. Using digital caliper, the thickness of the vertebral artery groove was measured to determine the feasibility of potential screw placement. OBJECTIVE: To determine the feasibility of screw insertion into the atlas lateral mass via the posterior arch. SUMMARY OF BACKGROUND DATA: The originally described starting point for atlas lateral mass screws, at the base of the lateral mass, can be associated with excessive bleeding and irritation of the greater occipital nerve. In order to avoid such problems, we routinely start the screw at a more cranial location on the dorsal, posterior-lateral arch of the atlas, when the anatomy permits. In cases where the arch is too small, we notch the undersurface of the arch so as to recess the screw into the notch. We undertook this cadaveric morphometric study to determine the feasibility of using such techniques in the general population. METHODS: A total of 709 atlas specimens were measured bilaterally to determine the thickness of the posterior-lateral arch at the level of the lateral mass. The presence of the ponticulus posticus was recorded as well. RESULTS: The average minimal thickness of the posterior-lateral atlas was 3.95 mm. There was a total of 157 complete and 34 incomplete ponticuli posticus. Overall, 85.2% of the specimens had a thickness greater than 3 mm, 654 (46.2%) greater than 4 mm, and 194 (13.7%) greater than 5 mm. CONCLUSIONS: Our results suggest that although only a small percentage of patients can accept a screw that is directly inserted via the posterior-lateral arch into the lateral mass, the notching technique is possible in the vast majority of patients. To our knowledge, this is the largest study to examine the possibility of using the posterior-lateral arch as the starting point for these screws. Our results suggest that alternative starting points for these screws are possible in a large percentage of the cases.

Black or African American↗
PubMed1976

Identification, classification and anatomical segregation of cells with X-like and Y-like properties in the lateral geniculate nucleus of old-world primates.

1. All the cells (158) that we studied in the lateral geniculate nuclei of Macaca nemestrina and Macaca irus could be distinguished as either X-like or Y-like on the basis of their responses to tests developed to classify cat retinal and lateral geniculate nucleus cells. These tests include responses to stationary spots, fast moving wands and moving gratings. 2. Response latencies to electrical stimulation of the optic chiasm were determined for 130 cells; no X-like cell showed a latency shorter than 1-7 ms, no Y-like cell showed a latency longer than 1-6 ms. Primate lateral geniculate nucleus cells with X-like properties thus receive their excitatory input from retinal cells with slowly conducting axons and these most probably include the tonic ganglion cells described by Gouras (1968, 1969); Y-like lateral geniculate nucleus cells are driven by retinal cells with faster conducting axons, most probably including the phasic ganglion cells described by Gouras. 3. Wiesel & Hubel (1966) classified monkey lateral geniculate nucleus cells into four main types based on their receptive-field properties, as revealed by spectrally and spatially distinct stimuli. We find that all Type I and Type II cells show X-like properties; all type IV cells show Y-like properties. Type III consists of a subtype that show X-like properties, here termed Type IIIx, and a subtype that show Y-like properties, here termed Type IIIy. 4. The first cells encountered as the micro-electrode reached the lateral geniculate nucleus were always X-like. In some penetrations only X-like cells were encountered as the electrode moved downward through the lateral geniculate nucleus. In the remaining penetrations, after recording X-like cells through most of the lateral geniculate nucleus, Y-like cells were then encountered. No X-like cells were found below Y-like cells. thus these two classes of cells are anatomically segregated within the primate lateral geniculate nucleus. Electrode marking showed the borger between X-like and Y-like cells to correspond to the border between the paro- and magnocellular layers of the lateral geniculate nucleus. Thus X-like cells (i.e. Types I, II and IIIx) occur in the parvocellular layers, Y-like cells (i.e. Types IIIy and IV)in the magnocellular layers.

Animals↗
PubMed2004

Right bundle-branch block ventricular tachycardias: septal versus lateral ventricular origin based on activation time to the right ventricular apex.

BACKGROUND: Identifying the septal versus lateral site of origin of ventricular tachycardia (VT) with a right bundle-branch block (RBBB)-type pattern and an R-S ratio >1 in lead V1 is difficult with the 12-lead ECG, especially in patients with prior apical infarction. METHODS AND RESULTS: We prospectively evaluated 58 patients with VT. Sixteen patients had apical infarcts (group 1), 29 had nonapical infarcts (group 2), and 13 had no heart disease (group 3). QRS complex onset to activation at the right ventricular apex (stim-RVA) was measured during left ventricular (LV) apical septal and lateral pacing, and 47 RBBB-type VTs (QRS-RVA) were localized to the septal or lateral apex by using entrainment techniques. Pacing and VT site of origin were confirmed by electroanatomic mapping. The stim-RVA time was 59+/-16 ms for septal versus 187+/-24 ms for lateral sites in group 1, P<0.001; 70+/-14 ms for septal versus 169+/-19 ms for lateral sites in group 2, P<0.001; and 42+/-15 ms for septal versus 86+/-16 ms for lateral sites in group 3, P<0.005. The QRS-RVA time was 50+/-13 ms for apical septal VTs versus 178+/-21 ms for lateral VTs in group 1, P<0.001; 71+/-17 ms for apical septal versus 157+/-20 ms for lateral VTs in group 2, P<0.001; and 32+/-12 ms for septal versus 71+/-16 ms for lateral VTs in group 3, P<0.01. CONCLUSIONS: The QRS-RVA differs for the VT site of origin from the LV septal versus lateral apex. These data prove useful in rapidly regionalizing the VT site of origin with a V1 R-S ratio >1, particularly in instances of an apical infarct, where surface ECG distinctions are less identifiable.

Aged↗