Biomedical subjects

R Mai

Publications and source records attributed to R Mai.

At least 19 recordsLinked to original sources

PubMed2007

An experimental in vivo analysis of the resorption to ultrasound activated pins (Sonic weld) and standard biodegradable screws (ResorbX) in sheep.

We compared the healing and reaction in the mandibles of 11 sheep of a conventional bioresorbable screw osteosynthesis with the newly developed ultrasound-activated pin osteosynthesis. The thermal stress caused by insertion of the ultrasound-aided pins leads to no cellular reaction around the pin. There is neither clinical nor histological evidence of any initial inflammation that could have been induced by the insertion. Adequate attachment of fibrous tissue to the pin head and the absence of any inflammation are important preconditions for the introduction of this new method of osteosynthesis into clinical practice. Further advantageous characteristics are easy intraoperative handling and a reduction in operating time, because cutting the thread is not required. There must be sufficient interlinkage of the polymer and the trabecular structures to ensure stability.

Absorbable Implants↗

PubMed2006

Surgical treatment of drug-resistant nocturnal frontal lobe epilepsy.

Of the cases with nocturnal frontal lobe epilepsy (NFLE) approximately 30% are refractory to antiepileptic medication, with several patients suffering from the effects of both ongoing seizures and disrupted sleep. From a consecutive series of 522 patients operated on for drug-resistant focal epilepsy, 21 cases (4%), whose frontal lobe seizures occurred almost exclusively (>90%) during sleep, were selected. All patients underwent a comprehensive pre-surgical evaluation, which included history, interictal EEG, scalp video-EEG monitoring, high-resolution MRI and, when indicated, invasive recording by stereo-EEG (SEEG). There were 11 males and 10 females, whose mean age at seizure onset was 6.2 years, mean age at surgery was 24.7 years and seizure frequency ranged from <20/month to >300/month. Nine patients reported excessive daytime sleepiness (EDS). Prevalent ictal clinical signs were represented by asymmetric posturing (6 cases), hyperkinetic automatisms (10 cases), combined tonic posturing and hyperkinetic automatisms (4 cases) and mimetic automatisms (1 case). All patients reported some kind of subjective manifestations. Interictal and ictal EEG provided lateralizing or localizing information in most patients. MRI was unrevealing in 10 cases and it showed a focal anatomical abnormality in one frontal lobe in 11 cases. Eighteen patients underwent a SEEG evaluation to better define the epileptogenic zone (EZ). All patients received a microsurgical resection in one frontal lobe, tailored according to pre-surgical evaluations. Two patients were operated on twice owing to poor results after the first resection. Histology demonstrated a Taylor-type focal cortical dysplasia (FCD) in 16 patients and an architectural FCD in 4. In one case no histological change was found. After a post-operative follow-up of at least 12 months (mean 42.5 months) all the 16 patients with a Taylor's FCD were in Engel's Class Ia and the other 5 patients were in Engel's Classes II or III. After 6 months post-surgery EDS had disappeared in the 9 patients who presented this complaint pre-operatively. It is concluded that patients with drug-resistant, disabling sleep-related seizures of frontal lobe origin should be considered for resective surgery, which may provide excellent results both on seizures and on epilepsy-related sleep disturbances. An accurate pre-surgical evaluation, which often requires invasive EEG recording, is mandatory to define the EZ. Further investigation is needed to explain the possible causal relationships between FCD, particularly Taylor-type, and sleep-related seizures, as observed in this cohort of NFLE patients.

Adolescent↗

PubMed2006

First clinical and biomechanical results of the Trochanteric Fixation Nail (TFN).

Conventional osteosynthesis of proximal femur fractures is still affected by serious complication rates between 4-18%, even though advanced implant modifications and surgical techniques are common practice. In terms of increasing age and co-morbidity of patients this complication ratio is expected to increase even further in the immediate future. One major reason for implant failure is the decreasing stability potential of the implant due to a loss in mechanical properties of cancellous bone. Therefore, efforts in new intramedulary techniques specifically focus on the load bearing characteristics of the implant by developing new geometries to improve the implant-tissue interface. This investigation discusses first clinical results of the trochanteric fixation nail TFN (145 patients) and a biomechanical analysis of the blade/femur head interaction under different static loading conditions. The TFN shows promising performance in first clinical results. In the clinical study the overall complication rate was significantly lower compared to other similar osteosynthesis. For the investigation of the biomechanical stability of the helical TFN blade the following experiments were performed: Analysis of the axial load required for insertion of the blade by free rotation; measurement of the corresponding rotation angle for total insertion (32 mm) (n = 8); pull-out forces with suppressed rotation (n = 4); loads for rotational overwinding of the implant in the fully inserted condition (n = 4). All investigations were performed on human femoral heads. The bone mineral densities of the specimens were detected by QCT-scans. Prior to cadaveric testing the experimental set-up was validated (n = 8) by the use of synthetic foam blocks (Sawbone).

Aged↗

PubMed2005

[Custom moldable hydroxyapatite collagen composite for repair of osseous defects].

AIM: In the following study we evaluated the biological response of a new freely moldable bone substitute in an animal model. MATERIAL AND METHODS: Critically sized defects were created surgically in the lower jaw of ten adult minipigs. The drill defects were filled with hydroxyapatite collagen paste. After observation periods of 1, 3, 6, 12, and 18 months the mandibles were harvested without wound healing defects for histological evaluation of resorption and bone ingrowth with a sawing and grinding technique. RESULTS: The result of the remodeling process was a complete degradation of hydroxyapatite collagen implants after 12-18 months with reorganization of vital trabeculae oriented in a mature pattern. CONCLUSION: The hydroxyapatite collagen cement works as an osteoconductor and shows signs of direct osseointegration and resorption.

Animals↗

PubMed2005

Intracerebral recordings of minor motor events, paroxysmal arousals and major seizures in nocturnal frontal lobe epilepsy.

The clinical features of nocturnal frontal lobe epilepsy (NFLE) consist of a spectrum of paroxysmal motor manifestations ranging from minor motor events (MMEs) to paroxysmal arousals (PAs) and major seizures. During MMEs and PAs scalp EEG generally does not show definite ictal abnormalities. We describe the clinical and electrophysiological features of three patients affected by drug-resistant NFLE studied with intracerebral electrodes during a presurgical evaluation. The stereo-EEG (SEEG) investigation revealed that MMEs can be fragments of the major seizure and occur during a brief epileptic discharge or on the following arousal. PAs, in the same subject, do not show a definite stereotypy despite the morphological and topographic similarity of the epileptic discharges, thus indicating that other variables may influence the clinical features of PAs.

Adult↗

PubMed2005

Sleep-related hyperkinetic seizures: always a frontal onset?

Hyperkinetic seizures are considered a typical manifestation of nocturnal frontal lobe epilepsy (NFLE). Patients with temporal lobe epilepsy with mainly sleep-related seizures have been described; however they commonly lack hyperkinetic activity and seizure frequency is low. We retrospectively analysed our population of 442 consecutive patients surgically treated between January 1996 and January 2004. Among these there were 25 patients with sleep-related hyperkinetic epileptic seizures, with a frontal lobe onset in 18 cases and a temporal lobe onset in 7. Patients with sleep-related hyperkinetic seizures with temporal lobe origin had anamnestic and clinical features strikingly similar to those with a frontal onset, with agitated movements, high seizure frequency and no history of febrile convulsions. We confirm our previous findings that this kind of epileptic manifestation is not only peculiar to frontal lobe epilepsy.

Adolescent↗

PubMed2005

An evaluation of resonance frequency analysis for the determination of the primary stability of orthodontic palatal implants. A study in human cadavers.

BACKGROUND: The primary stability of short orthodontic implants is important for anchorage. METHODS: For this study 14 cadaveric human heads were used. The stability of orthodontic implants (Straumann) with lengths of 4 and 6 mm and different localization (palatal suture or paramedially) were evaluated. The implants with length of 6 mm were only placed in the suture and primary stability was non-invasively determined with the resonance frequency (Osstell). The invasive method for the analysis of the morphometric parameters of the implant/bone contact was carried out by means of histological and radiological examinations. RESULTS: The 6 mm implants have significant better primary stability in the palatal suture as 4 mm implants paramedially (P<0.05). No differences were found between 6 and 4 mm implants in the palatal suture and between 4 mm implants in palatal suture to paramedially. The histological and radiological results demonstrate the ability to measure the implant stability by investigation of the bone offer and density around the implant. Bone structure, especially the pore size in the trabecular bone and the precision of placement may influence the stability. CONCLUSION: This study shows that the short implant gives sufficient bone fixation, independently of placement. The quality of implantation and bone structure are more important than the length of the orthodontic implant.

Bone Density↗

PubMed2005

X-ray microanalysis of elements in the masticatory muscle after paresis of the right masseter.

Muscle activity and function appear to be related to ionic concentrations in the muscle. We investigated whether muscle paresis induced by injection of Botulinum toxin A (Botox) in 16-week-old pigs over a 56-day period is associated with ionic changes in the affected muscles. Tissue samples were taken from the masseter, temporalis, medial pterygoid, and geniohyoid muscles by a standardized method and used for energy-dispersive x-ray microanalysis in an environmental scanning electron microscope. The largest increase in Na(+) was measured in the right and left sides of the masseter muscle in treated animals. Additionally, a significant elevation of Na(+) was measured in the anterior part of the temporalis muscle and in the pterygoid muscle (P < 0.05). In temporalis and pterygoid muscles, an increase in sulfur in both sides of treated pigs' heads was observed. Botox((R)) has an indirect impact on ion concentrations, resulting in changes in muscle functional capacity and adaptive compensation of paretic muscle function by other muscles.

Animals↗

PubMed2004

Electroclinical, MRI and neuropathological study of 10 patients with nodular heterotopia, with surgical outcomes.

We present the results of a retrospective study on 10 patients operated on for intractable epilepsy associated with nodular heterotopia as identified by high resolution MRI. Seven patients had unilateral heterotopia, one patient had symmetric bilateral heterotopia and two patients had asymmetric bilateral heterotopia. By stereo-electroencephalogram (SEEG) (nine patients) interictal activity within nodules was similar in all cases, and ictal activity never started from nodules alone but from the overlying cortex or simultaneously in nodules and cortex. Excellent outcomes (Engel class Ia, 1987) were achieved in the seven patients with unilateral heterotopia, showing that surgery can be highly beneficial in such cases when the epileptogenic zone is carefully located prior to surgery by MRI and particularly SEEG. For the bilateral cases surgical outcomes were Engel IIa (one patient) or Engel IIIa (two patients). Histological/immunohistochemical studies of resected specimens showed that all nodules had similar microscopic organization, even though their extent and location varied markedly. The overlying cortex was dysplastic in nine patients, but of normal thickness. We suggest that nodule formation may be the result of a dual mechanism: (i) failure of a stop signal in the germinal periventricular region leading to cell overproduction; and (ii) early transformation of radial glial cells into astrocytes resulting in defective neuronal migration. The intrinsic interictal epileptiform activity of nodules may be due to an impaired intranodular GABAergic system.

Adult↗

PubMed2004

Sleep-related hyperkinetic seizures of temporal lobe origin.

Sleep-related hyperkinetic seizures are a common feature of nocturnal frontal lobe epilepsy. Although sleep-related seizures with a temporal lobe origin have been reported, they commonly lack hyperkinetic activity. The authors describe three patients with sleep-related seizures characterized by frenetic, agitated, hyperactive movements (bimanual/bipedal activity, rocking, axial, pelvic, and hemiballistic movements), in whom stereo-EEG investigation and surgical outcome demonstrated a temporal lobe origin of the attacks.

Adult↗

PubMed2003

[Preoperative determination of the position of mandibular canal for planning sagittal ramus osteotomy of the mandible].

BACKGROUND: In the literature the incidence of permanent nerve lesions ranges from 3 to 39%. Therefore, we think that it is necessary to discuss the procedure of individual risk assessment and management. Standard imaging techniques for the preoperative planning and preparation of a sagittal split osteotomy usually include a panoramic radiograph and lateral cephalometric radiograph. If an assessment of the transversal thickness of the lower jaw and cortical substance is required, or the position of the inferior alveolar nerve needs to be determined for preoperative planning, computed tomography of the viscerocranium has to be performed. By employing the conventional computed tomographic X-ray imaging system CommCAT, we are able to determine preoperatively both the transversal thickness of the lower jaw including the cortical substance and the diameter of the ascending ramus of the mandible at the proximal osteotomy site. PATIENTS AND METHOD: We examined prospectively the value of these additional investigations and compared them with the intraoperative findings in 29 patients. With these tomograms, the relation between the position of the inferior alveolar nerve and the vestibular cortical bone was metrically evaluated. In 17 of 58 jaw sides we detected the nerve at a distance from the outer cortical bone of 2 mm or less. The situation for the upper osteotomy was critical in eight cases where the thickness of the mandibular ramus was only 3 mm. RESULTS: By using of the conventional computed tomography system CommCAT, we have the preoperative opportunity to determine the transversal thickness of the mandibular ramus as well as the exact position of the inferior alveolar nerve and its distance from the cortical bone of the mandibular corpus. By predicting the nerve's position and its relation to the osteotomy site, we are able to individualize the operation procedure so that a high standard of safety can be achieved.

Adolescent↗

PubMed2003

A neuropathological, stereo-EEG, and MRI study of subcortical band heterotopia.

The authors performed an MRI, stereo-EEG, and pathology study on a woman with subcortical band heterotopia and partial epilepsy. Clinical manifestations of seizures always started when ictal discharges were present in outer and heterotopic cortices. Simultaneous activation of both cortices and presence of differentiated neurons in the white matter and the heterotopia strongly suggest that the cortices were anatomically and functionally interconnected.

Adult↗

PubMed2003

Surgery for drug resistant partial epilepsy in children with focal cortical dysplasia: anatomical-clinical correlations and neurophysiological data in 10 patients.

OBJECTIVE: To analyse a population of children with focal cortical dysplasia operated on for drug resistant partial epilepsy, with emphasis on clinical features, seizure semiology, interictal and ictal EEG and stereo EEG findings, histological and topographical characteristics of the lesions, extension and localisation of cerebral excision, and its postoperative effect on seizure frequency. METHODS: 10 patients were studied, aged between 26 months and 11 years (median 6 years). Magnetic resonance imaging (MRI) abnormalities were unilobar (temporal 3, frontal 2), bilobar (2), or multilobar (1); the two patients with negative MRI suffered from frontal seizures. Presurgical diagnostic steps varied in complexity and invasiveness depending on the anatomical/electrical/clinical features of each patient. In four patients they included only scalp video EEG monitoring, and in six, also invasive recordings using stereotactically implanted intracerebral electrodes. Surgery consisted of corticectomy plus lesionectomy in all cases. RESULTS: 70% of the patients were seizure-free after a minimum postoperative follow up of 25 months. These included three patients with temporal lesions and four of seven patients with other lobar or multilobar extratemporal localisation. One patient had improvement in seizure control. Outcome was poor in multilobar patients, but a class Ia outcome was obtained in one case after partial lesionectomy associated with bilobar corticectomy. All patients showed developmental improvement. CONCLUSIONS: Analysis of the data in these patients allowed the production of an "anatomical-clinical concordance" list, which appeared to be correlated with the diagnostic steps performed. Carrying out a stereo EEG exploration in the most complex cases proved useful in defining the epileptogenic zone in extratemporal and multilobar epilepsies. Stereo EEG recordings facilitated a tailored resection of extralesional cortex.

Cerebral Cortex↗

PubMed2002

Focal cortical dysplasia: neuropathological subtypes, EEG, neuroimaging and surgical outcome.

Since the original description by Taylor, the term focal cortical dysplasia has been used to refer to a wide range of alterations of the cortical mantle. More recently, these conditions have been described from neuroimaging, neuropathological and genetic standpoints, generating several classifications. It is widely recognized that these classifications are unsatisfactory. We propose a simplified classification of focal cortical dysplasias based on easily recognized neuropathological characteristics. We retrospectively re-examined histological sections of cortex from 52 of 224 (23%) patients operated on for drug-resistant partial epilepsy in which cortical dysplasia was present but not associated with other brain pathologies except hippocampal sclerosis. Three subgroups were identified: (i) architectural dysplasia (31 patients) characterized by abnormal cortical lamination and ectopic neurones in white matter; (ii) cytoarchitectural dysplasia (six patients) characterized by giant neurofilament-enriched neurones in addition to altered cortical lamination; and (iii) Taylor-type cortical dysplasia (15 patients) with giant dysmorphic neurones and balloon cells (all but two patients) associated with cortical laminar disruption. The patients with architectural dysplasia had lower seizure frequency than those with cytoarchitectural and Taylor-type dysplasia, and the epileptogenic zone was mainly in the temporal lobe. In patients with Taylor-type dysplasia, the epileptogenic zone was mainly extratemporal, and interictal stereo-EEG was distinctive. MRI was unrevealing in 34% of patients, but distinctive signal alterations characterized most patients with Taylor-type dysplasia, while focal hypoplasia with MRI abnormalities was found in architectural dysplasia. Patients with Taylor-type dysplasia had the best outcome, with 75% seizure-free (Engel class Ia) after at least a year of follow-up compared with 50% of cytoarchitectural dysplasia and 43% of architectural dysplasia patients seizure-free. This three-category classification is based on easily recognized histopathological characteristics and avoids complicated terminology, while the distinctive ensemble of other characteristics defines clinically homogeneous groups.

Adult↗

PubMed2000

Circulating levels of tumour necrosis factor-alpha and its soluble receptors are increased in the blood of patients with amyotrophic lateral sclerosis.

An immunologic pathogenesis for amyotrophic lateral sclerosis (ALS) has been recently proposed. We tested the whole tumour necrosis factor (TNF) system in the serum of 51 ALS patients at different stages of the disease and 36 healthy controls. Antigenic TNF-alpha and its soluble receptors (sTNF-Rs), measured by ELISA, were significantly higher in ALS patients than in healthy controls. However, biologically active TNF-alpha, corresponding to the sTNF-Rs-unbound trimeric TNFalpha molecule and assayed by its cytotoxic activity on a sensitive cell line, was similar between ALS patients and healthy controls. Neither antigenic TNF-alpha, bioactive TNF-alpha nor sTNF-Rs correlated with disease severity, disease duration, or weight loss. In conclusion, we reported an activation of the TNF system in ALS. The role of this activation in the pathogenesis of the disease remains elusive.

Amyotrophic Lateral Sclerosis↗

PubMed2000

[What is the value of the Denecke surgical therapy concept in deglutition disorders?].

BACKGROUND: Denecke developed 1957 a surgical strategy consisting of three or four operative steps for rehabilitation of patients with unilateral paralysis of IXth and Xth cranial nerve. These four steps are the following: myotomy of the cricopharyngeal muscle, resection of the paralyzed pharyngeal wall, medialization of the paralyzed vocal cord and fixation of the soft palate to the posterior pharyngeal wall which can be facultative. PATIENTS AND METHODS: For the first time we have reviewed patients operated on with the Denecke operation in a retrospective study. The surgical results should be analyzed to deduce some parameters for surgical indication. RESULTS: 16 patients were reviewed in regard to nourishment status, situation of tracheostomy, former pneumonias, classification of Miller and Eliachar for aspiration and subjective evaluation. The follow-up was 21 +/- 16 months postoperatively. In 8 cases surgical intervention was successful. In 2 additional cases the results were partially satisfying. CONCLUSIONS: The surgical procedure of Denecke was successful for improving substantially nourishment and aspiration status of considerably reduced patients in about 50% of the reviewed cases. Preoperative cinematography of swallowing, manometry and an interdisciplinary approach are required to clearly define the indications for surgical intervention.

Adult↗

PubMed2000

Experience from a multidisciplinary "dizzy" clinic.

OBJECTIVE: To describe the experience of a combined otolaryngology and neurology multidisciplinary clinic in the evaluation, investigation, and management of patients with dizziness. STUDY DESIGN: Prospective clinical study. SETTING: Patients were seen in a tertiary referral, multidisciplinary clinic at The Toronto Hospital, University of Toronto, Ontario, Canada. INTERVENTION: A thorough history, formal otoneurologic examination, and appropriate laboratory investigations were performed. After their assessment, the patient's diagnoses were classified as peripheral, central, psychogenic, or undiagnosed and were then subdivided into specific clinical diagnoses. RESULTS: The first 812 consecutive patients seen in the multidisciplinary clinic from January 1, 1993 to December 31, 1998 are reported. Five hundred twenty-five (64.7%) patients were found to have a peripheral vestibular cause for their dizziness, 66 (8.1%) had a central cause, 108 (13.3%) had a diagnosis unknown, and 73 (9.0%) were thought to be psychogenic. In 40 (4.9%) patients, a peripheral and central cause were found. More than one type of peripheral disorder was noted in 17.9% of patients with a peripheral vestibular cause for their dizziness, and 12.3% of patients with a central cause for their dizziness had more than one specific type of central nervous system disorder. CONCLUSIONS: Most patients that were seen in a multidisciplinary clinic had a peripheral vestibular disorder. Central causes of dizziness were relatively uncommon. Serious diseases such as tumor, multiple sclerosis, and encephalitis were rare and unlikely to present with dizziness only. It is important to realize that a patient may have more than one type of disorder accounting for the symptoms, which may represent a spectrum of disease affecting the inner ear.

Adolescent↗

PubMed2000

Clinical ictal symptomatology and anatomical lesions: their relationships in severe partial epilepsy.

High-resolution imaging techniques can demonstrate anatomic alterations in most patients identified as candidates for surgical treatment of their partial epilepsy. The demonstration of an anatomic lesion is only one step in the presurgical diagnostic procedure, which includes video-EEG and, when necessary, video-stereo-EEG recordings of seizures. A review of the literature shows that the simple removal of the magnetic resonance imaging (MRI)-evident lesion ("lesion-ectomy") reduces but does not completely suppress seizures in a large percentage of patients, especially those with neuronal migration disorders. This phenomenon could, at least in part, be explained by preliminary data (in 33 patients) showing that less than 20% of seizures correspond to a well-localized, intralesional discharge in about 40% of stereo-EEG-investigated patients with at least one intralesional electrode. The authors illustrate some anatomo-electroclinical examples of intraindividual variability of the ictal symptomatology, raising the problem of the decision about the extent of the surgical removal. Recent histologic and immunohistochemical studies have demonstrated several kinds of structural alterations in the stereo-EEG-defined epileptogenic zone, not always overlapping with the MRI-visible lesion. This aspect can further explain some failures of MRI-guided lesionectomies. That relationships between "lesions" and epileptogenic zones may be variable is also suggested by reports of patients who present with multiple lesions (i.e., cavernous angiomas, Bourneville syndrome) and are cured by removal of only one of them.

Adult↗