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N Papadakis

Publications and source records attributed to N Papadakis.

At least 19 recordsLinked to original sources
PubMed2004

Diffusion tensor imaging for the assessment of upper motor neuron integrity in ALS.

BACKGROUND: High angular resolution diffusion tensor imaging (HARD) is an MRI technique that exploits the mobility of water molecules to yield maps of structural order and directionality of white matter tracts with greater precision than six-direction diffusion tensor imaging (DTI) schemes. OBJECTIVE: To assess whether HARD is more sensitive than conventional MRI or neurologic assessment in detecting the upper motor neuron (UMN) pathology of patients with ALS. METHODS: Twenty-five patients with definite UMN clinical signs and 23 healthy volunteers underwent conventional MRI. HARD datasets were collected from a subset of these participants plus four patients with isolated lower motor neuron (LMN) signs. ALS symptom severity was assessed by a neurologist, the conventional MR images were reviewed by neuroradiologists, and the DTI maps were subject to quantitative region of interest analysis. RESULTS: Motor cortex hypointensity on T2-weighted images and corona radiata hyperintensity on proton density-weighted images distinguished patients with UMN involvement from volunteers with 100% specificity, but only 20% sensitivity. Fractional anisotropy (FA) was reduced in the posterior limb of the internal capsule in patients with UMN involvement compared to volunteers. A FA threshold value with a sensitivity of 95% to detect patients with ALS (including those with isolated LMN signs) had a specificity of 71%. CONCLUSIONS: High angular resolution diffusion tensor imaging may be more sensitive than conventional MRI or neurologic assessment to the upper motor neuron (UMN) pathology of ALS, but it lacks the specificity required of a diagnostic marker. Instead, it is potentially useful as a quantitative tool for monitoring the progression of UMN pathology.

Adult↗
PubMed2002

New robust 3-D phase unwrapping algorithms: application to magnetic field mapping and undistorting echoplanar images.

The phase, as well as the magnitude, of MRI images can carry useful information. It may be used to encode flow or temperature, or to map the magnetic field for the undistorting of EPIs and automated shimming. In all cases, we measure the extra spin given to nuclei. Unfortunately, we can only measure the final phase of the spins: the rotation is wrapped into the range [-pi, +pi], and to obtain a measure of the parameter of interest the missing multiples of 2pi must be replaced--a process known as phase unwrapping. While simple in principle, standard phase unwrapping algorithms fail catastrophically in the presence of even small amounts of noise. Here we present a new algorithm for robust three-dimensional phase unwrapping, in which unwrapping is guided, so that it initially works on less noisy regions. We test the algorithm on simulated phase data, and on maps of magnetic field, which were then used to successfully undistort EPI images. The unwrapping algorithm could be directly applied to other kinds of phase data.

Acoustic Stimulation↗
PubMed2001

Cross-cultural study of symptom expectation following minor head injury in Canada and Greece.

OBJECTIVES: The purpose of the present study is to compare the frequency and nature of expected symptoms in Greece (a country where the chronic post-concussive syndrome is largely unknown) with that in Canada. METHODS: A symptom checklist was administered to two subject groups selected from local companies in Patras, Greece, and Edmonton, Canada, respectively. Subjects were asked to imagine having suffered head trauma with loss of consciousness in a motor vehicle accident and to check off symptoms, they expected might arise from the injury. For symptoms they anticipated, they were asked to select the period of time they expected those symptoms to persist. RESULTS: In both the Greek and Edmontonian groups, the pattern of symptoms anticipated closely resembled the acute symptoms commonly reported by accident victims with minor head injury. Yet, while many Edmontonians also anticipated symptoms to last months or years, very few Greek subjects selected any symptoms as being likely to persist in a chronic manner. CONCLUSIONS: In Greece, despite the frequent experience of minor head injury in motor vehicle accidents, there is a very low rate of expectation of any chronic sequelae from such an injury, contrasting greatly with the response shown in Canada, where the prevalence of the chronic post-concussive syndrome is higher. Symptom expectation in some countries may be an important factor in the development of the chronic post-concussive syndrome.

Adult↗
PubMed2001

Responses of human frontal cortex to surprising events are predicted by formal associative learning theory.

Learning depends on surprise and is not engendered by predictable occurrences. In this functional magnetic resonance imaging (fMRI) study of causal associative learning, we show that dorsolateral prefrontal cortex (DLPFC) is associated specifically with the adjustment of inferential learning on the basis of unpredictability. At the outset, when all associations were unpredictable, DLPFC activation was maximal. This response attenuated with learning but, subsequently, activation here was evoked by surprise violations of the learned association. Furthermore, the magnitude of DLPFC response to a surprise event was sensitive to the relationship that had been learned and was predictive of subsequent behavioral change. In short, the physiological response properties of right DLPFC satisfied specific predictions made by associative learning theory.

Adult↗
PubMed2000

In vivo proton magnetic resonance spectroscopy of brain tumors.

The ability of magnetic resonance spectroscopy (MRS) to differentiate neoplastic brain cells and their metabolic and structural characteristics is evaluated. We examined 120 patients with brain tumors using a 1.5-tesla MRI unit and MRS. The peak areas of N-acetyl-aspartate (NAA), phosphocreatine-creatine (Pcr-Cr), choline-containing compounds (Cho), lactate, lipids, myoinositol, amino acids and the ratios of NAA/Pcr-Cr, NAA/Cho and Cho/Pcr-Cr were calculated by a standard integral algorithm. In normal brain tissue, the following metabolites were identified: NAA at 2.0 ppm, Pcr-Cr at 3.0 ppm and Cho at 3.2 ppm. The different concentrations of the metabolites examined and their role in the biochemical profile of different types of tumors are discussed. The confidence interval of the MRS versus pathology was between 0.9 and 0.954, while it was between 0.52 and 0.631 for MRI versus pathology. The Cho/Pcr-Cr ratio is a very important malignancy marker for histologic tumor grading of astrocytomas. The greater this ratio, the higher the grade of the astrocytoma. NAA/Pcr-Cr together with Cho/Pcr-Cr help specify the presence or absence of a neoplasm. Proton MRS is a useful and promising diagnostic modality not only in diagnosing but also in grading solid brain tumors.

Adult↗
PubMed1999

Whiplash injury.

Explore the source record for details and available documents.

Adolescent↗
PubMed1999

Whiplash.

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Culture↗
PubMed1998

Post traumatic paraplegics living in Athens: the impact of pressure sores and UTIs on everyday life activities.

This paper contains the findings of a scientific research which was done on post-traumatic paraplegics who live in the area of Athens. Greece, and measured the impact of pressure sores and UTIs on their everyday life activities. The target population was 127 individuals out of which 98 were observed and interviewed. A semi-structured questionnaire which consisted of two parts used; the first part of the questionnaire included general questions whereas the second contained the Sarno Functional Life Scale (SFLS) which is a tool measuring the level of independence of disabled people. Sixty-two per cent of the population was male. The mean age of the sample population at the time they had the accident which caused the paraplegia was 31.5, while the median was 28.5. The majority of the subjects comes from the lower socioeconomic class. Traffic accidents accounted for the 55% of the occurrences of paraplegia, falls for 37%, surgical complication for 4% and athletic activities for the remaining 4%. Forty-nine percent of the sample had been hospitalised in a rehabilitation centre. However, the multiple regressions used did not reveal any statistically significant relation between the hospitalisation in a rehabilitation centre and the paraplegic's scores in any of the Sarno Functional Life Scale's (SFLS) variables. Instead, the multiple regressions employed yielded paraplegics' scores in the SFLS's everyday life activities that were negatively related to age (P = 0.004) and pressure sores (P = 0.021). The paraplegics' scores on the SFLS's indoors activities are positively related to the years since injury (P = 0.048) and health education on daily fluid consumption (P = 0.003). The scores of the subjects on the SFLS's outdoor activities are positively related to the years of education (P = 0.008), the years since injury (P = 0.011), while are negatively related to pressure sores (P = 0.034) and UTIs (0.044). The subjects' scores on the SFLS variables regarding social relations had a negative relation to sex, (female) (P = 0.0001), age (P = 0.001) and pressure sores (P = 0.019), while they have a positive relation with the years since injury (P = 0.024).

Activities of Daily Living↗
PubMed1998

Internuclear ophthalmoplegia following minor head injury: a case report.

Internuclear ophthalmoplegia (INO) is a common sign of multiple sclerosis in young patients and of vascular diseases in older people. Traumatic bilateral internuclear ophthalmoplegia following severe head injuries may occur. We present the unusual case of a young patient suffered from bilateral INO as an isolated finding after a minor head injury, without other signs of brain stem or cortical injury. The ophthalmoplegia has persisted for 22 months.

Accidental Falls↗
PubMed1996

Craniofacial osteotomies to facilitate resection of large tumours of the anterior skull base.

Large tumours of the anterior cranial fossa can be a major challenge to the neurosurgeon or the maxillofacial surgeon. However, skull base approaches facilitate their resection. We describe our experience with the extended subfrontal approach in treating tumours of the anterior cranial base. This approach was performed on 29 patients with large tumours of the anterior skull base. The final outcome in all 29 patients was favourable in terms of total resection of the tumour with minimal subsequent neurological deficit. Two patients developed transient oedema of the frontal lobes without persistent neurological sequelae. Another patient developed a postoperative cerebrospinal fluid fistula that was successfully repaired. The patients were followed for a period ranging from 6 to 28 months. There was no recurrence. The operative technique is described. En bloc removal of the roofs of the orbits and part of the anterior cranial fossa permits wide exposure of the lesion with minimal brain retraction. Reconstruction of the anterior cranial base should be meticulous to avoid cerebrospinal fluid leaks and subsequent meningitis. Loss of smell is a sequel to this approach. The possible risks and some important technical details are highlighted.

Adenoma↗
PubMed1994

Spinal bone mineral density changes following halo vest immobilization for cervical trauma.

In this prospective study we followed the bone mineral density (BMD) changes of the injured cervical spine immobilized with the halo vest. In order to define the natural history of cancellous vertebral bone loss and restoration, dual-energy densitometry was used on each of ten selected cervical spines in the lateral view (1) immediately after the application of the device, (2) at the end of the treatment and (3) 3 months after the removal of the halo vest. The halo vest produces local osteoporosis in the immobilized cervical spine with an overall reduction of BMD averaging 2.83% (P < 0.05). The response of the cervical spine to immobilization was only slightly different from patient to patient and between different vertebral bodies in each particular spine. The type and the level of injury of the cervical spine were not related to the changes of BMD, age or gender of the patient, whereas the local osteoporosis was mostly reversible in the follow-up evaluation of 5-6 months.

Absorptiometry, Photon↗
PubMed1994

Pattern reversal visual evoked potentials in minor head injury.

Pattern reversal visual evoked potentials (PR-VEPs) have been recorded in 50 patients with minor head injury (MHI) on days 1 and 30 after trauma and the data compared to 20 normals. None of the patients had visual complaints. The aim was to investigate a possible visual pathway affection in MHI and test the usefulness of PR-VEPs as an objective noninvasive tool in the detection of a possible subclinical affection of the visual system in MHI. P100 latency and amplitude had no significant difference compared to normals. Comparison of patient data on days 1 and 30 after trauma showed a significant latency decrease and amplitude increase on day 30, compared to day 1. These alterations were not age dependent. Our data suggest affection of the human visual pathway in MHI. PR-VEP recording seems to be a useful, objective, noninvasive tool, helping to identify possible subclinical affections of the visual pathway in MHI.

Adolescent↗
PubMed1991

Penetration of ciprofloxacin into human cerebrospinal fluid in patients with inflamed and non-inflamed meninges.

The penetration of ciprofloxacin into the cerebrospinal fluid (CSF) in 25 patients with non-inflamed meninges and in 9 patients with inflamed meninges was studied. In the patients with non-inflamed meninges plasma and CSF were obtained 1-10 h after the second dose of ciprofloxacin and in the patients with inflamed meninges 1, 2, 3, 5, 7 and 9 h after the second dose. In the first group (non-inflamed meninges) data from 6 patients were obtained 4, 5 and 6 h post-dose. Mean ciprofloxacin concentrations in the CSF ranged from 0.073 mg/l to 0.106 mg/l during this observation time, while in the second group (inflamed meninges) they ranged from 0.089 to 0.260 mg/l. These results demonstrate that ciprofloxacin diffuses into the CSF at concentrations which exceed the MICs of Neisseria meningitidis and most gram-negative aerobic bacilli.

Adolescent↗
PubMed1981

Changes in brain surface pH during acute isocapnic metabolic acidosis and alkalosis.

It has been thought that the blood-brain barrier is relatively impermeable to changes in arterial blood H+ and OH- concentrations. We have measured the brain surface pH during 30 min of isocapnic metabolic acidosis or alkalosis induced by intravenous infusion of 0.2 N HCl or NaOH in anesthetized dogs. The mean brain surface pH fell significantly by 0.06 and rose by 0.04 pH units during HCl or NaOH infusion, respectively. Respective changes were also observed in the calculated cerebral interstitial fluid [HCO-3]. There were no significant changes in cisternal cerebrospinal fluid acid-base variables. It is concluded that changes in arterial blood H+ and OH- concentrations are reflected in brain surface pH relatively quickly. Such changes may contribute to acute respiratory adaptations in metabolic acidosis and alkalosis.

Acidosis↗
PubMed1981

Reversal of experimental delayed cerebral vasospasm by angiotensin-converting enzyme inhibition.

Delayed cerebral vasospasm is an important determinant of the clinical outcome after subarachnoid hemorrhage, but its prevention and treatment has met with limited success. Since cerebral arteries were found to be sensitive to the vasoconstrictor effect of angiotensin II, the possibility of angiotensin's contribution to this vasospasm was investigated. Delayed cerebral arterial spasm was documented angiographically 72 hours after introduction of blood in the subarachnoid space of dogs. Following injection of the angiotensin-converting enzyme inhibitor, teprotide, repeat cineangiograms at 30, 60, and 90 minutes demonstrated partial or total release of spasm of the basilar artery and its branches. It is concluded that angiotensin II participates in the delayed cerebral vasospasm after hemorrhage, and that angiotensin inhibition may release the spasm and prevent cerebral ischemia.

Angiography↗