PubMed Health⌕ Search

Biomedical subjects

Jamshid Ghajar

Publications and source records attributed to Jamshid Ghajar.

12 recordsLinked to original sources
PubMed2006

A quantitative synchronization model for smooth pursuit target tracking.

We propose a quantitative model for human smooth pursuit tracking of a continuously moving visual target which is based on synchronization of an internal expectancy model of the target position coupled to the retinal target signal. The model predictions are tested in a smooth circular pursuit eye tracking experiment with transient target blanking of variable duration. In subjects with a high tracking accuracy, the model accounts for smooth pursuit and repeatedly reproduces quantitatively characteristic patterns of the eye dynamics during target blanking. In its simplest form, the model has only one free parameter, a coupling constant. An extended model with a second parameter, a time delay or memory term, accounts for predictive smooth pursuit eye movements which advance the target. The model constitutes an example of synchronization of a complex biological system with perceived sensory signals.

Attention↗
PubMed2006

Increased oculomotor deficits during target blanking as an indicator of mild traumatic brain injury.

Given the susceptibility of cerebellar-cortical tracts to shearing injury from traumatic brain injury (TBI), we investigated impairment in the generation of predictive eye movements and its relationship to cognitive deficits in mild TBI patients using a smooth pursuit target-blanking paradigm. Compared to a target-tracking paradigm without blanking, this paradigm more greatly necessitates the generation of predictive eye movements, which are subserved by brain regions involved in cognitive processing. Mild TBI patients showed impaired prediction of target trajectories during target blanking, demonstrated by generation of saccades at earlier and more variable time points, as well as greater and more variable oculomotor error compared to controls. In addition, California Verbal Learning Test (CVLT-II) scores related to working memory, learning, and executive function were more highly correlated with oculomotor variability during target blanking than during target tracking. Our results suggest that a disruption of cerebellar-cortical connections in TBI may account for both oculomotor and cognitive impairment, and that measures of predictive eye movements during target blanking may be a sensitive metric of cognitive deficits after mild TBI.

Adolescent↗
PubMed2006

Deficits in predictive smooth pursuit after mild traumatic brain injury.

Given that even mild traumatic brain injury (TBI) may produce extensive diffuse axonal injury (DAI), we hypothesized that mild TBI patients would show deficits in predictive smooth pursuit eye movements (SPEM), associated with impaired cognitive functions, as these processes are dependent on common white matter connectivity between multiple cerebral and cerebellar regions. The ability to predict target trajectories during SPEM was investigated in 21 mild TBI patients using a periodic sinusoidal paradigm. Compared to 26 control subjects, TBI patients demonstrated decreased target prediction. TBI patients also showed increased eye position error and variability of eye position, which correlated with decreased target prediction. In all subjects, average target prediction, eye position error and eye position variability correlated with scores related to attention and executive function on the California Verbal Learning Test (CVLT-II). However, there were no differences between TBI and control groups in average eye gain or intra-individual eye gain variability, or in performance on the Wechsler Abbreviated Scale of Intelligence (WASI), suggesting that the observed deficits did not result from general oculomotor impairment or reduced IQ. The correlation between SPEM performance and CVLT-II scores suggests that predictive SPEM may be a sensitive assay of cognitive functioning, including attention and executive function. This is the first report to our knowledge that TBI patients show impaired predictive SPEM and eye position variability, and that these impairments correlate with cognitive deficits.

Adolescent↗
PubMed2006

Direct transport within an organized state trauma system reduces mortality in patients with severe traumatic brain injury.

BACKGROUND: Prehospital management of traumatic brain injury (TBI) and trauma system development and organization are aspects of TBI care that have the potential to significantly impact patient outcome. This multi-center study was conducted to explore the effect of prehospital management decisions on early mortality after severe TBI. METHODS: This report is based on 1449 patients with severe TBI (GCS<9) treated at 22 trauma centers enrolled in a New York State quality improvement (QI) program between 2000 and 2004. The prehospital data collected on these patients include time of injury, time of arrival to the trauma center, mode of transport, type of EMS provider, direct or indirect transport, blood pressure and pulse oximetry values, GCS score, pupillary assessment, and airway management procedures. RESULTS: After exclusion criteria were applied, a total of 1,123 patients were eligible for analysis. The majority of patients were male (75%) with a mean age of 36 years. After controlling for arterial hypotension, age, pupillary status, and initial GCS score, direct transport was found to result in significantly lower mortality than indirect transport. Transport mode, time to admission, and prehospital intubation were not found to be related to 2-week mortality. CONCLUSIONS: The present study provides class II evidence that demonstrates a 50% increase in mortality associated with indirect transfer of TBI patients. Patients with severe TBI should be transported directly to a Level I or Level II trauma center with capabilities as delineated in the Guidelines for the Prehospital Management of Traumatic Brain Injury, even if this center may not be the closest hospital.

Adult↗
PubMed2006

Surgical management of traumatic parenchymal lesions.

INDICATIONS: Patients with parenchymal mass lesions and signs of progressive neurological deterioration referable to the lesion, medically refractory intracranial hypertension, or signs of mass effect on computed tomographic (CT) scan should be treated operatively. Patients with Glasgow Coma Scale (GCS) scores of 6 to 8 with frontal or temporal contusions greater than 20 cm3 in volume with midline shift of at least 5 mm and/or cisternal compression on CT scan, and patients with any lesion greater than 50 cm3 in volume should be treated operatively. Patients with parenchymal mass lesions who do not show evidence for neurological compromise, have controlled intracranial pressure (ICP), and no significant signs of mass effect on CT scan may be managed nonoperatively with intensive monitoring and serial imaging. TIMING AND METHODS: Craniotomy with evacuation of mass lesion is recommended for those patients with focal lesions and the surgical indications listed above, under Indications. Bifrontal decompressive craniectomy within 48 hours of injury is a treatment option for patients with diffuse, medically refractory posttraumatic cerebral edema and resultant intracranial hypertension. Decompressive procedures, including subtemporal decompression, temporal lobectomy, and hemispheric decompressive craniectomy, are treatment options for patients with refractory intracranial hypertension and diffuse parenchymal injury with clinical and radiographic evidence for impending transtentorial herniation.

Craniocerebral Trauma↗
PubMed2006

Surgical management of posterior fossa mass lesions.

INDICATIONS: Patients with mass effect on computed tomographic (CT) scan or with neurological dysfunction or deterioration referable to the lesion should undergo operative intervention. Mass effect on CT scan is defined as distortion, dislocation, or obliteration of the fourth ventricle; compression or loss of visualization of the basal cisterns, or the presence of obstructive hydrocephalus. Patients with lesions and no significant mass effect on CT scan and without signs of neurological dysfunction may be managed by close observation and serial imaging. TIMING: In patients with indications for surgical intervention, evacuation should be performed as soon as possible because these patients can deteriorate rapidly, thus, worsening their prognosis. METHODS: Suboccipital craniectomy is the predominant method reported for evacuation of posterior fossa mass lesions, and is therefore recommended.

Brain↗
PubMed2006

Surgical management of depressed cranial fractures.

INDICATIONS: Patients with open (compound) cranial fractures depressed greater than the thickness of the cranium should undergo operative intervention to prevent infection. Patients with open (compound) depressed cranial fractures may be treated nonoperatively if there is no clinical or radiographic evidence of dural penetration, significant intracranial hematoma, depression greater than 1 cm, frontal sinus involvement, gross cosmetic deformity, wound infection, pneumocephalus, or gross wound contamination. Nonoperative management of closed (simple) depressed cranial fractures is a treatment option. TIMING: Early operation is recommended to reduce the incidence of infection. METHODS: Elevation and debridement is recommended as the surgical method of choice. Primary bone fragment replacement is a surgical option in the absence of wound infection at the time of surgery. All management strategies for open (compound) depressed fractures should include antibiotics.

Disease Management↗
PubMed2006

Surgical management of acute epidural hematomas.

INDICATIONS FOR SURGERY: An epidural hematoma (EDH) greater than 30 cm3 should be surgically evacuated regardless of the patient's Glasgow Coma Scale (GCS) score. An EDH less than 30 cm3 and with less than a 15-mm thickness and with less than a 5-mm midline shift (MLS) in patients with a GCS score greater than 8 without focal deficit can be managed nonoperatively with serial computed tomographic (CT) scanning and close neurological observation in a neurosurgical center. TIMING: It is strongly recommended that patients with an acute EDH in coma (GCS score < 9) with anisocoria undergo surgical evacuation as soon as possible. METHODS: There are insufficient data to support one surgical treatment method. However, craniotomy provides a more complete evacuation of the hematoma.

Disease Management↗
PubMed2006

Surgical management of acute subdural hematomas.

INDICATIONS FOR SURGERY: An acute subdural hematoma (SDH) with a thickness greater than 10 mm or a midline shift greater than 5 mm on computed tomographic (CT) scan should be surgically evacuated, regardless of the patient's Glasgow Coma Scale (GCS) score. All patients with acute SDH in coma (GCS score less than 9) should undergo intracranial pressure (ICP) monitoring. A comatose patient (GCS score less than 9) with an SDH less than 10-mm thick and a midline shift less than 5 mm should undergo surgical evacuation of the lesion if the GCS score decreased between the time of injury and hospital admission by 2 or more points on the GCS and/or the patient presents with asymmetric or fixed and dilated pupils and/or the ICP exceeds 20 mm Hg. TIMING: In patients with acute SDH and indications for surgery, surgical evacuation should be performed as soon as possible. METHODS: If surgical evacuation of an acute SDH in a comatose patient (GCS < 9) is indicated, it should be performed using a craniotomy with or without bone flap removal and duraplasty.

Disease Management↗
PubMed2002

Clinical trials in head injury.

Traumatic brain injury (TBI) remains a major public health problem globally. In the United States the incidence of closed head injuries admitted to hospitals is conservatively estimated to be 200 per 100,000 population, and the incidence of penetrating head injury is estimated to be 12 per 100,000, the highest of any developed country in the world. This yields an approximate number of 500,000 new cases each year, a sizeable proportion of which demonstrate significant long-term disabilities. Unfortunately, there is a paucity of proven therapies for this disease. For a variety of reasons, clinical trials for this condition have been difficult to design and perform. Despite promising pre-clinical data, most of the trials that have been performed in recent years have failed to demonstrate any significant improvement in outcomes. The reasons for these failures have not always been apparent and any insights gained were not always shared. It was therefore feared that we were running the risk of repeating our mistakes. Recognizing the importance of TBI, the National Institute of Neurological Disorders and Stroke (NINDS) sponsored a workshop that brought together experts from clinical, research, and pharmaceutical backgrounds. This workshop proved to be very informative and yielded many insights into previous and future TBI trials. This paper is an attempt to summarize the key points made at the workshop. It is hoped that these lessons will enhance the planning and design of future efforts in this important field of research.

Brain Injuries↗
PubMed2002

Predictors of compliance with the evidence-based guidelines for traumatic brain injury care: a survey of United States trauma centers.

BACKGROUND: In 1995, evidence-based guidelines for the management of severe traumatic brain injury (TBI) were published and disseminated. Information regarding their implementation is limited. METHODS: During 1999 to 2000, we contacted all designated U.S. trauma centers caring for adults with severe TBI to determine the degree of guideline compliance and to identify predictors. RESULTS: Of 924 centers identified, 828 participated (90%). Four hundred thirty-three with intensive care units caring for severe TBI were surveyed. Three hundred ninety-five centers transferring patients were excluded. Full guideline compliance was rare (n = 68 [16%]). In multivariate analyses, treatment protocols (odds ratio [OR], 3.6; 95% confidence interval [CI], 1.9-6.6), neurosurgery residency program (OR, 5.0; 95% CI, 2.6-9.8), and state (OR, 2.7; 95% CI, 0.62-12) or American College of Surgeons (OR, 5.1; 95% CI, 1.1-23) designation increased the likelihood of full compliance versus noncompliance. CONCLUSION: Although evidence-based guidelines were published and disseminated in 1995, implementation is infrequent. Focus must turn to changing physician practice and transport decisions to provide guideline-compliant care and improve patient outcome.

Brain Injuries↗