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Interventions and service need following mild and moderate head injury: the Oxford Head Injury Service.

OBJECTIVE: To describe the interventions given by the Oxford Head Injury Service (OXHIS) to patients seen after head injury, predominantly mild or moderate, over the first six months after their injuries. DESIGN: Descriptive data of the amounts of early intervention provided by OXHIS in relation to severity of head injury and the amount of service need identified at six month follow-up. SETTING: OXHIS aimed to register all patients aged 16-65 with a head injury of any severity, resident in Oxfordshire. It contacted and provided interventions for a random half of those registered at 7-10 days post-injury as part of a randomized controlled trial to investigate the effectiveness of early follow-up. At six months post-injury, independent assessment of all those registered was undertaken to evaluate outcome and identify continuing service needs. SUBJECTS: The data come from the 579 patients (of the 1156 registered), randomized to receive the new service at 7-10 days post-injury. All but eight of these received some form of service, and 252 of the randomized patients were available for interview at six months post-injury to assess their continuing service need. RESULTS: In the first five months after head injury: 240 patients received postal information alone and were not otherwise in contact with the service; 127 had telephone contact, advice and information; 93 were seen in person, assessed and given advice and information; 78 needed more help and support from the OXHIS team over the telephone; and 33 required further face-to-face contact either from OXHIS or other services. Extensive use was made of standardized leaflets but only accompanied by individualized assessment and advice. At six months 252 of the 579 patients were interviewed: 101 had no problems; 136 needed further reassurance; and 15 required further intervention. Patients with longer periods of post-traumatic amnesia (PTA) were more likely to receive a higher level of service, but the majority of patients who received the more extensive services were those with 'mild' and 'moderate' head injuries. CONCLUSIONS: Although the amount of service provided at 7-10 days post-injury increased with severity of head injury, most service was in fact given to patients with milder head injuries which were much more common. The majority of patients seen at six months post-injury needed reassurance, advice or other services, and monitoring of patients for some time after their head injuries does seem warranted. A population of 560,000 people could receive service from three whole-time equivalent (WTE) staff using these assessment and management protocols.

Adolescent↗

Depression among the head-injured and non-head-injured: a discriminant analysis.

Neuropsychologists often use traditional psychological tests to assess depression following a head injury; but the assumption that depression with a head injury resembles that in an uninjured person is suspect. The current study attempts to examine the cognitive manifestations of depression with and without a coexisting head-injury. Advanced statistical methods are used to assess whether or not the two depressions 'look alike' with respect to the neuropsychological sequelae of the disorders. A total of 1182 people were entered into one of two discriminant function analyses (DFA) for depression. Each person was a member of one of the following groups: (a) depressed, (b) non-depressed, (c) head-injured, or (d) head-injured and depressed. Two functions were performed for depression, one on the population of head-injured people and one on the population of uninjured people. Cross-validations were performed for each population and across populations in order to assess the utility of each population's function for the opposite group. This comparison allows the researcher to indirectly compare depression in the two populations. Both functions were successfully applied to either population when MMPI variables were included in the analyses. However, when only cognitive variables were included the function performed on the non-head-injured population did not correctly classify head-injured people as depressed or non-depressed. One explanation for this is that the range of cognitive scores in head-injured people is so great that it allows for a less accurate but more generalizable function. Suggestions for future research are discussed.

Adult↗

Effect of head elevation on intracranial pressure, cerebral perfusion pressure, and cerebral blood flow in head-injured patients.

The traditional practice of elevating the head in order to lower intracranial pressure (ICP) in head-injured patients has been challenged in recent years. Some investigators argue that patients with intracranial hypertension should be placed in a horizontal position, the rationale being that this will increase the cerebral perfusion pressure (CPP) and thereby improve cerebral blood flow (CBF). However, ICP is generally significantly higher when the patient is in the horizontal position. This study was undertaken to clarify the issue of optimal head position in the care of head-injured patients. The effect of 0 degree and 30 degrees head elevation on ICP, CPP, CBF, mean carotid pressure, and other cerebral and systemic physiological parameters was studied in 22 head-injured patients. The mean carotid pressure was significantly lower when the patient's head was elevated at 30 degrees than at 0 degrees (84.3 +/- 14.5 mm Hg vs. 89.5 +/- 14.6 mm Hg), as was the mean ICP (14.1 +/- 6.7 mm Hg vs. 19.7 +/- 8.3 mm Hg). There was no statistically significant change in CPP, CBF, cerebral metabolic rate of oxygen, arteriovenous difference of lactate, or cerebrovascular resistance associated with the change in head position. The data indicate that head elevation to 30 degrees significantly reduced ICP in the majority of the 22 patients without reducing CPP or CBF.

Adult↗

[A comparative study of the characteristics of femoral hip prosthesis heads--study and results ceramic-coated hip joint heads of titanium].

Today, only hard/soft cup and femoral head combinations are employed for hip joint prostheses. Highly polished ceramic is a material with very good tribological properties for femoral heads, being highly resistant to mechanical wear and tear, and highly resistant to chemical reactions in the biological environment. The advantage of metal heads, in contrast, undoubtedly lies in their resistance to breakage and the ease with which their geometry can be modified with respect, for example, to antirotation angle and neck length. The ideal material for femoral heads is a combination of the two materials. The new multi-layer combination of titanium-niobium oxide/nitride ceramic coating applied to a prehardened titanium head combines the positive material properties in an ideal manner. Femoral heads made of CoCrMo, oxide-hardened titanium, aluminium oxide or multilayer titanium-niobium ceramic were compared by means of friction an wear and tear tests. The TiNb-ceramic-metal heads showed similar abrasion at the surface as the ceramic heads. At the high loads of more than 400 kp, which may also be reached under physiological conditions, the specially coated titanium-ceramic heads proved to be superior in terms of resistance to fracture and tribological properties.

Biomechanical Phenomena↗

Progressive collapse of transposed necrotic area after transtrochanteric rotational osteotomy for osteonecrosis of the femoral head induces osteoarthritic change. Mid-term results of transtrochanteric rotational osteotomy for osteonecrosis of the femoral head.

INTRODUCTION: Osteonecrosis of the femoral head is usually progressive, and once collapse of the femoral head develops, joint destruction almost invariably follows. Therefore, for partial osteonecrosis of the femoral head, various types of osteotomies have been developed in an attempt to save the femoral head and maintain the natural function of the hip joint. MATERIALS AND METHODS: We reviewed 25 hips in 21 patients for a mean follow-up period of 6.4 years after Sugioka's transtrochanteric anterior rotational osteotomy for osteonecrosis of the femoral head. RESULTS: The clinical results were excellent or good in 20 hips (80%), and radiological success was observed in 15 hips (60%) with an absence of both collapse of the newly established weight-bearing area of the femoral head and narrowing of the joint space. Progressive collapse of the transposed necrotic area was noted in 10 hips (40%), and of these 10 hips, narrowing of the joint space was observed in 7 (70%) at follow-up. A significant correlation was demonstrated between progressive collapse of the transposed necrotic area and narrowing of the joint space. Growth of an osteophyte of the femoral head was observed postoperatively in 16 hips (64%), particularly at anterior and lateral sites of the femoral head. CONCLUSIONS: Though collapse of a new weight-bearing area can be prevented, progressive collapse of the transposed necrotic area induces anterior joint instability, giving rise to osteoarthritic change. It is therefore concluded that prevention of the collapse of the transposed necrotic area is important for satisfactory long-term results.

Adult↗

Stroke affects the coordination and stabilization of head, thorax and pelvis during voluntary horizontal head motions performed in walking.

OBJECTIVE: This study was conducted to investigate and compare the coordination and stabilization of axial segments during walking with and without horizontal voluntary head turns, in healthy (n=5) and hemiparetic (n=10) subjects. METHODS: Subjects were instructed to turn the head as fast and as soon as possible in the direction indicated by an illuminated arrow signal (right, left or none) that was triggered at initial contact of the right (healthy) or paretic (hemiparetic) foot. Head, thorax, and pelvis motions were obtained from a 9-segment model using retro-reflective markers and a Vicon-512 system with 6 high-resolution cameras. Coordination of axial segments in the horizontal plane was characterized using cyclographs and cross-correlation analyses. Stabilization of the segments was quantified using root mean square (RMS) values of the segment's normalized acceleration profile. RESULTS: The healthy subjects showed a direction-dependent modulation of axial segment coordination, with head turns toward and away from the stance limb favoring and hindering, respectively, the contra-rotational pattern of the thorax with respect to the pelvis during locomotion. Meanwhile, pelvis motions remained unaltered. This direction-specific modulation pattern was disrupted in the hemiparetic subjects, both in the spatial and temporal domains. Moreover, larger RMS values for head and thorax segments were observed in the hemiparetic groups, both with and without the superimposition of voluntary head motions. CONCLUSIONS: The findings suggest that: (1) head rotations during walking modify axial segment coordination in a direction-specific manner, (2) the pelvic rotations associated with locomotion remained unaffected by head rotations and (3) stroke alters this coordination behavior, which may contribute to balance dysfunctions during locomotion.

Aged↗

Positional reproducibility of the patient's head normalized by a robotized chair-based automatic head-positioning system, Racs-N.

With a view to normalization of the head orientation without the use of a fixation jig for the measurement of jaw movement employing an X-ray television, we have been developing an automatic head-positioning system, Racs-N, consisting of a head-position sensor and a robotized chair. The head position is monitored in 6 degrees of freedom (d.o.f.) by using a position-sensitive detector (PSD) camera-based photostereometry. If they are incorrect, the robotized chair rectifies them automatically by adjusting the position and orientation of the head support in 5 d.o.f. (except the vertical position). The rectified position, however, has a certain margin of error, due to the mobility of the head relative to the head support. To improve this, we employed an iterative correction in that the positioning is repeated until the determined position converges. In experiments employing several subjects, this particular correction was verified to converge by more than six iterations and to be effective for the reduction of head-position errors.

Adult↗

The Performance Status Scale for Head and Neck Cancer Patients and the Functional Assessment of Cancer Therapy-Head and Neck Scale. A study of utility and validity.

BACKGROUND: The goal of this investigation was to examine the relationship between, and application of, two disease specific quality of life (QL) measures currently being employed for head and neck cancer patients: the Functional Assessment of Cancer Therapy-Head and Neck Scale (FACT-H&N) and the Performance Status Scale for Head and Neck Cancer Patients (PSS-HN). METHODS: The FACT-H&N and PSS-HN were administered to 151 head and neck cancer patients with a range of disease sites, treatment status (on vs. off treatment), and treatment modalities (surgery, radiation, and chemotherapy). RESULTS: FACT-H&N subscale and total scores and PSS-HN subscale scores proved sensitive to patients groups (showed significant and clinically meaningful differences) on the basis of treatment status (on vs. off treatment) and global performance status (Karnofsky scores). The pattern of correlations between FACT-H&N and PSS-HN subscales supported the scales' construct (convergent vs. divergent) validity. The strongest and most significant associations were observed between PSS-HN Normalcy of Diet and Eating in Public, and the head and neck subscale (HNS) of FACT-H&N, both of which were designed to measure the unique problems of head and neck cancer patients. More modest associations were observed between subscales measuring physical and functional areas of performance, social functioning, and emotional well-being. CONCLUSIONS: The FACT-HNS was found to be reliable and valid when applied to head and neck cancer patients. It clearly adds information to that collected by the parent (core) instrument. The PSS-HN also provides unique information, independent of that provided by the Karnofsky or the FACT-H&N. This study supported the multidimensional nature of QL for head and neck cancer patients, and thus the importance of assessing disease specific concerns in addition to general health status when assessing functional and QL outcome.

Adolescent↗

The relationship between ortho head posture and head posture measured during walking.

Murphy, Preston, and Evans recognized the dynamic nature of head posture and developed instrumentation capable of measuring and recording this posture in a continuous manner. The aim of the current project was to use the newly developed instrumentation to determine whether the difference is statistically significant between the mean natural head ortho posture, measured in a controlled manner, and the mean dynamic head posture obtained during 5 minutes of walking activity in an experimental situation. The mean ortho head posture and the mean walking head posture were measured in each of 30 men. The differences between these two sets of mean head postures were statistically significant (p < or = 0.05). In 23 persons, the mean walking head posture was tipped backward relative to the mean natural head ortho position.

Adult↗

Derivation of the children's head injury algorithm for the prediction of important clinical events decision rule for head injury in children.

BACKGROUND: A quarter of all patients presenting to emergency departments are children. Although there are several large, well-conducted studies on adults enabling accurate selection of patients with head injury at high risk for computed tomography scanning, no such study has derived a rule for children. AIM: To conduct a prospective multicentre diagnostic cohort study to provide a rule for selection of high-risk children with head injury for computed tomography scanning. DESIGN: All children presenting to the emergency departments of 10 hospitals in the northwest of England with any severity of head injury were recruited. A tailor-made proforma was used to collect data on around 40 clinical variables for each child. These variables were defined from a literature review, and a pilot study was conducted before the children's head injury algorithm for the prediction of important clinical events (CHALICE) study. All children who had a clinically significant head injury (death, need for neurosurgical intervention or abnormality on a computed tomography scan) were identified. Recursive partitioning was used to create a highly sensitive rule for the prediction of significant intracranial pathology. RESULTS: 22,772 children were recruited over 2 1/2 years. 65% of these were boys and 56% were <5 years old. 281 children showed an abnormality on the computed tomography scan, 137 had a neurosurgical operation and 15 died. The CHALICE rule was derived with a sensitivity of 98% (95% confidence interval (CI) 96% to 100%) and a specificity of 87% (95% CI 86% to 87%) for the prediction of clinically significant head injury, and requires a computed tomography scan rate of 14%. CONCLUSION: A highly sensitive clinical decision rule is derived for the identification of children who should undergo computed tomography scanning after head injury. This rule has the potential to improve and standardise the care of children presenting with head injuries. Validation of this rule in new cohorts of patients should now be undertaken.

Algorithms↗

Mechanisms controlling human head stabilization. I. Head-neck dynamics during random rotations in the horizontal plane.

1. Potential mechanisms for controlling stabilization of the head and neck include voluntary movements, vestibular (VCR) and proprioceptive (CCR) neck reflexes, and system mechanics. In this study we have tested the hypothesis that the relative importance of those mechanisms in producing compensatory actions of the head-neck motor system depends on the frequency of an externally applied perturbation. Angular velocity of the head with respect to the trunk (neck) and myoelectric activity of three neck muscles were recorded in seven seated subjects during pseudorandom rotations of the trunk in the horizontal plane. Subjects were externally perturbed with a random sum-of-sines stimulus at frequencies ranging from 0.185 to 4.11 Hz. Four instructional sets were presented. Voluntary mechanisms were examined by having the subjects actively stabilize the head in the presence of visual feedback as the body was rotated (VS). Visual feedback was then removed, and the subjects attempted to stabilize the head in the dark as the body was rotated (NV). Reflex mechanisms were examined when subjects performed a mental arithmetic task during body rotations in the dark (MA). Finally, subjects performed a voluntary head tracking task while the body was kept stationary (VT). 2. Gains and phases of head velocity indicated good compensation to the stimulus in VS and NV at frequencies < 1 Hz. Gains dropped and phases advanced between 1 and 2 Hz, suggesting interference between neural and mechanical components. Above 3 Hz, the gains of head velocity increased steeply and exceeded unity, suggesting the emergence of mechanical resonance.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

Mechanisms controlling human head stabilization. II. Head-neck characteristics during random rotations in the vertical plane.

1. In this study we have tested the hypothesis that the mechanisms controlling stabilization of the head-neck motor system can vary with both the frequency and spatial orientation of an externally applied perturbation. Angular velocity of the head with respect to the trunk (neck) and myoelectric activity of two neck muscles (semispinalis capitis and sternocleidomastoid) were recorded in eight seated subjects during pseudorandom rotations of the trunk in the vertical (pitch) plane. Subjects were externally perturbed with a random sum-of-sines stimulus at frequencies ranging from 0.35 to 3.05 Hz. Four instructional sets were presented. Voluntary mechanisms were examined by having the subjects actively stabilize the head in the presence of visual feedback as the body was rotated (VS). Visual feedback was then removed, and the subjects attempted to stabilize the head in the dark as the body was rotated (NV). Reflex mechanisms were examined when subjects performed a mental arithmetic task during body rotations in the dark (MA). Finally, subjects performed a voluntary head tracking task while the body was kept stationary (VT). 2. In VS and NV, gains and phases of head velocity indicated good compensation for the perturbation at frequencies up to 2 Hz. Between 2 and 3 Hz, gains dropped slowly and then steeply descended above 3 Hz as phases became scattered. 3. In MA, gains were lower and exhibited more scatter than in VS and NV at frequencies < 1 Hz. Phases around -180 degrees indicated that compensatory activity was occurring even with these low gains. Between 1 and 2 Hz, response gains steeply ascended, implying that reflex mechanisms were becoming the predominant mechanism for compensation in this frequency range. Above 2 Hz, gains dropped off to 0.5 and lower, but phases remained close to -180 degrees, suggesting that the reflex mechanisms were not dominant in this frequency range, but that they were still contributing toward compensation for the trunk perturbation. 4. Neck muscle electromyographic (EMG) responses were similar in VS, NV, and MA, demonstrating decreasing gains between 0.35 and 1.5 Hz, and then increasing beyond the previous high level of activation. This U-shaped response pattern implies an enhanced participation of neural mechanisms, probably of reflex origin, in the higher frequency range. 5. Patterns observed during external perturbations of the trunk were not apparent in the response dynamics of voluntary head tracking. In VT, subjects successfully tracked the stimulus only at the lowest frequencies of head movement.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗

[Electromyographic study on the effects of head position to head and neck muscles].

The purpose of this study is to reveal the relationship between the head position, and the neck and head muscles. At 4 head positions, the activities of masseter, anterior temporal, anterior digastric, sternocleidomastoid and trapezius muscle of ten normal subjects standing straight were investigated electromyographically with surface electrodes during voluntary maximal clenching in centric occlusion. Head positions were right tilting, left tilting, up-right and natural head position. The results obtained were as follows; 1. During head tilting, the activities of anterior digastric and sternocleidomastoid muscle on the tilting side were increased, the activities of masseter and trapezius muscle on the opposite side of the tilting side were increased, the activity of the anterior temporal muscle did not vary from the activity during up-right head position. 2. During natural head position, only the activity of sternocleidomastoid muscle on the natural tilting side was increased.

Electromyography↗

Rhythmical eye-head-torso rotation alters fore-aft head stabilization during treadmill locomotion in humans.

A repetitive manoeuvre called torso rotation (TR) is known to temporarily reduce the gain of the horizontal vestibulo-ocular reflex by 10-15% in healthy humans. TR consists of a series of rhythmical rotations of the eyes, head and upper body executed continuously for 30 minutes while standing. Our aim was to investigate whether TR affects the ability to hold the head in a fixed fore-aft position relative to space while walking on a treadmill with eyes closed. Ten healthy subjects stood in a carefully standardized position on a stationary treadmill. The treadmill started unexpectedly and ran for 4 s at 29 cm/s. The test stimulus was a linear acceleration in the fore-aft direction at the moment of treadmill start-up. Linear head position (i.e., ability to stabilize the head) was measured during and following the stimulus. A mechanical system prevented head rotation. Two series of 60 trials were performed before TR (control 1 and control 2 series) and one after TR. Before TR, subjects drifted rearward at an average drift velocity +/- S.D. = 3.1 +/- 0.9 cm/s. This drift was reasonably stable over time within and between the two control series. After TR, head holding ability was further impaired, with subjects having more difficulty to stabilize their head after treadmill start-up. In the first 10 trials after the arrest of TR, the average drift velocity was significantly larger than before TR(6.1 +/- 1.5 cm/sec, p < 0.01). Recovery to control values followed a roughly exponential time course, with 67% recovery occurring in the first 3.4 minutes after TR. Our results indicate that TR impairs the ability to sense and/or respond to fore-aft linear accelerations of the head following treadmill start-up in the absence of vision.

Adult↗

Duodenal-preserving resection of the head of the pancreas and pancreatic head resection with second-portion duodenectomy for benign lesions, low-grade malignancies, and early carcinoma involving the periampullary region.

HYPOTHESIS: Duodenal-preserving resection of the head of the pancreas (DPRHP) and pancreas head resection with segmental duodenectomy (PHRSD) can be alternatives to standard pancreaticoduodenectomy for benign periampullary lesions. DESIGN: Retrospective analysis of patients requiring surgery for benign and borderline malignant tumors of the periampullary region. SETTING: Tertiary care referral center. PATIENTS: Duodenal-preserving resection of the head of the pancreas (n = 8) and PHRSD (n = 7) were performed in 15 patients with a preoperative diagnosis of benign and borderline malignant tumors of the periampullary region (ie, 11 pancreas head lesions [2 intraductal papillary mucinous tumors, 4 serous cystadenomas, 2 insulinomas, 1 epidermal cyst, 1 metastatic renal cell carcinoma, 1 nonfunctioning islet cell tumor/parapaillary] and 4 duodenal lesions [3 adenomas and 1 adenocarcinoma]). MAIN OUTCOME MEASURES: Surgical factors (operation time and blood loss), postoperative complication, postoperative pancreatic insufficiency (eg, development of diabetes mellitus and steatorrhea or elevated stool elastase values), weight change, and recurrence of disease. RESULTS: No differences were noted in the mean operation time and estimated blood loss between the 2 procedures. Major postoperative complication constituted the following: bile duct stricture (n = 1) in DPRHP and delayed gastric emptying (n = 1) and postoperative bleeding (n = 1) in PHRSD. Newly developed diabetes mellitus occurred in 1 patient. Exocrine pancreatic insufficiency (steatorrhea) was observed in 1 patient after PHRSD. Patients with early duodenal carcinoma and intraductal papillary mucinous tumors with a borderline malignancy are still alive without evidence of recurrence. There was no hospital or long-term mortality. CONCLUSIONS: Duodenal-preserving resection of the head of the pancreas is recommended first for a benign or low-grade, early malignant pancreatic head lesion; PHRSD can be an option for a lesion of the ampullary-parapapillary duodenal area as well as the pancreatic head. Duodenal-preserving resection of the head of the pancreas can be converted to PHRSD if ischemia of the second portion of the duodenum occurs. We found benign periampullary lesions could be conservatively treated with DPRHP and PHRSD, which could substitute for classic pancreaticoduodenectomy.

Adult↗

Therapeutic hypothermia for head injury.

BACKGROUND: Mild to moderate induced hypothermia has been used in the treatment of head injury for over 50 years, although few randomised controlled trials have been performed. Recent encouraging results from small, single-centre trials and consistent findings of a cerebral protection effect of cooling in laboratory models of global ischaemia has led to a renewed interest in the area. OBJECTIVES: To determine whether the use of mild therapeutic hypothermia in the treatment of moderate and severe head injury improves short-term control of intracranial pressure (ICP) and long-term functional outcome. SEARCH STRATEGY: Electronic searches of the Injuries Group trial registry and EMBASE for any relevant randomised trials, supplemented by hand searching of conference proceedings and reference lists of relevant articles. SELECTION CRITERIA: All randomised controlled trials of mild hypothermia versus control (open or normothermia) in the treatment of patients with any closed head injury requiring hospitalisation. Mild hypothermia was defined as local or systemic cooling to a target temperature of at most 34-35 degrees Celsius for a period of at least 12 hours. Outcome was all-cause mortality and death or severe disability at the end of the scheduled follow-up period. All trials were assessed by two reviewers, and included or excluded on a consensus basis. DATA COLLECTION AND ANALYSIS: Eleven potential trials of therapeutic hypothermia for head injury were found, of which two are ongoing and one is awaiting assessment. The eight remaining trials were included in the systematic review. Data on death, GOS score at final follow-up, complications and ICP were sought and extracted, either from published material or by contact with the investigators. Mantel-Haenzel odds ratios and 95% confidence intervals were calculated for death and death and severe disability for each trial on an intention-to-treat basis. No quantitative synthesis of data on either complications or ICP was attempted. Trials of immediate and deferred hypothermia were analysed separately. MAIN RESULTS: Active immediate hypothermic treatment was associated with a 33% non-significant (p=0.16) reduction in the odds of death at the end of treatment or final follow-up, (OR 0.67, 95% confidence interval 0.38 to 1.17), and a 61% reduction (p=0.004) in the odds of being dead or severely disabled, (OR 0.39, 95% confidence interval 0.20 to 0.74). Similar effect sizes were found for delayed hypothermia. These results are, however, based on a few small trials each of less than 100 patients. A multi-centre trials of hypothermia versus control in 392 patients will be reporting results in 1999, providing substantially more evidence than is currently available. REVIEWER'S CONCLUSIONS: Although this review would suggest a strong positive effect of therapeutic hypothermia, the results are based on several small trials carried out in single, specialist centres. The results of a large multi-centre trial are expected in 1999 and will more than treble the available evidence. Until these results have been released, it would be inappropriate to make any short-term recommendations for clinical practice or research.

Craniocerebral Trauma↗

Headful packaging revisited: the packaging of more than one DNA molecule into a bacteriophage P1 head.

Like a variety of other bacteriophages, such as T4 and P22, bacteriophage P1 packages DNA by a "headful" mechanism in which the capacity of the viral capsid determines the size of the single DNA molecule that is packaged. Because of the long-standing and general acceptance of this packaging mechanism, we were surprised to discover that some of our observations, using the in vitro P1 packaging system, could be explained by the packaging of less than headful-sized (< 110 kb) DNA molecules into a P1 capsid. To account for these observations, we describe results that support a model of in vitro P1 packaging in which multiple less than headful-sized DNA molecules are taken into a P1 head until that head has been filled. The results further suggest that the phage so generated can occasionally inject more than one DNA molecule into a cell upon viral infection. The data that supports these conclusions are: (1) the DNAs of the circular P1 cloning vectors pAd10sacBII (32 kb) and pNS358 (14 kb) are packaged in vitro with an efficiency of about 6 to 12% of that of longer concatemers of these DNAs. (2) The in vitro packaging of two differentially marked, less than 18 kb plasmid DNAs in the same reaction results in the production of a phage that can occasionally inject both DNAs into the same cell upon infection. (3) Virus particles generated by the packaging of either pAd10sacBII plasmid DNA or the two differently marked plasmids have a density in CsCl equilibrium gradients that is the same as P1 plaque-forming phage, suggesting that the former phage contain a headful of DNA. These results cannot be explained by Cre-mediated site-specific recombination between plasmids in the P1 packaging extracts. Finally, we present in vivo experiments that are also consistent with the headful packaging of multiple DNAs into a P1 head.

Bacteriophage P1↗

Stimulation of the superior colliculus in the alert cat. II. Eye and head movements evoked when the head is unrestrained.

Electrical stimulation of the superior colliculus (SC) in alert cats free to move their head, evoked coordinate eye and head movements. The characteristics of these movements as well as their mode of coordination differed according to the collicular region being explored. Three zones were distinguished. In the anterior zone, evoked eye saccades were retinotopic and the accompanying head movements were slow and small in amplitude. The vestibular slow phase velocity signal was continuously added to the eye saccadic command so that the evoked gaze shift was identical, with the head fixed or free. In the intermediate zone, evoked eye saccades were goal-directed and the synchronous head movements fast and of large amplitude. The vestibular slow phase signal was cancelled during the eye saccade so that the evoked gaze shift was the result of the eye plus head angular displacement. In the posterior zone, the evoked head movements were goal-directed. The pattern of eye movements was similar to a vestibular nystagmus. This zone probably directly commands body orienting movements. A model of SC function in gaze orienting behavior is proposed, calling upon at least two different modes of eye-head coordination.

Animals↗