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Biomedical subjects

M A Leonard

Publications and source records attributed to M A Leonard.

16 recordsLinked to original sources
PubMed2001

Comparison of frameless stereotactic systems: accuracy, precision, and applications.

OBJECTIVE: Frameless stereotactic systems have become an integral part of neurosurgical practice. At our center, we recently introduced for clinical use a small, portable, frameless stereotactic system, namely the Cygnus PFS system (Compass International, Rochester, MN). The purpose of this study was to compare the accuracy of the Cygnus PFS system with that of two larger systems that are also currently in use at our institution, i.e., the SMN system (Zeiss, Oberkochen, Germany) and the ISG viewing wand (ISG Technologies, Toronto, Canada). These systems represent three kinds of frameless stereotactic technologies that are commercially available. Each system uses a different method of spatial localization, i.e., mechanical linkage (ISG system), magnetic field digitization (Cygnus system), or optical technology (SMN system). METHODS: Using a stereotactic "phantom," we measured the accuracies of all three systems with identical data sets. The errors in localization in three-dimensional space for nine targets were calculated by using 10 magnetic resonance imaging data sets. The precision of each system was also calculated. RESULTS: With this experimental protocol, the Cygnus system attained a mean accuracy of 1.90 +/- 0.7 mm, the ISG viewing wand system a mean accuracy of 1.67 +/-0.43 mm, and the SMN microscope a mean accuracy of 2.61 +/- 0.99 mm. The precision values were not significantly different among the systems. CONCLUSION: We observed only small differences in accuracy and precision among these three systems. We briefly review the advantages and disadvantages of each system and note that other factors, such as portability, ease of use, and microscope integration, should influence the selection of a frameless stereotactic system.

Humans↗
PubMed1999

Cervical spondylotic myelopathy: patterns of neurological deficit and recovery after anterior cervical decompression.

OBJECTIVES: We evaluated the specific pattern of pre- and postoperative neurological signs and symptoms and functional results in patients with cervical spondylotic myelopathy who underwent anterior decompressive operations. Additionally, we sought to determine which findings had predictive value for surgical outcome. METHODS: We retrospectively reviewed the records of 76 patients with cervical spondylotic myelopathy caused by osteophytic ridge or intervertebral disc herniation who underwent anterior cervical decompression and fusion performed by one surgeon. The patients were evaluated postoperatively by office visits and/or telephone interviews. Outcome was assessed by objective neurological examination and scoring with multiple functional rating scales. RESULTS: The most common preoperative symptoms were deterioration of hand use (75%), upper extremity sensory complaints (82.9%), and gait difficulties (80.3%). In the upper extremities, preoperative weakness was most common in the hand intrinsic muscles (56.6%) and triceps (28.9%), and in the lower extremities, preoperative weakness was most common in the iliopsoas (38.8%) and quadriceps (26.3%). In the lower extremities, individual muscle groups had strength improvement rates from 79.1 to 88.1 %; somewhat higher rates, from 81.3 to 90.9%, were observed in the upper extremities. When evaluated by using the Cooper myelopathy scale, lower extremity functional improvement occurred in 46.7% of the patients and upper extremity functional improvement in 75.4%. Overall functional improvement, evaluated by using a modification of the Japanese Orthopedic Association Scale, was noted in 79.7% of the patients who had abnormal scores preoperatively. CONCLUSION: Strength improved at rates of approximately 80 to 90% in individual muscle groups after anterior cervical decompression. However, fewer than half of all patients experienced functional improvement in the lower extremities, a discrepancy that was probably caused by persistent spasticity rather than muscle weakness. Postoperative dysfunction in the upper extremities was caused by residual weakness as well as sensory loss. Recurrent symptomatic spondylosis at unoperated levels was calculated to occur at an incidence of 2% per year.

Adult↗
PubMed1991

Four fibroblast tropomyosin isoforms are expressed from the rat alpha-tropomyosin gene via alternative RNA splicing and the use of two promoters.

cDNA clones encoding four rat tropomyosin isoforms, termed TM-2, TM-3, TM-5a, and TM-5b, were isolated and characterized. All are derived from the alpha-tropomyosin gene via alternative RNA processing and the use of two alternate promoters. The cDNA sequences predict that TM-2 and TM-3 both contain 284 amino acids and differ from each other only at an internal region of the protein from amino acids 189 through 213, due to alternative splicing of exons 6a and 6b. TM-5a and TM-5b both contain 248 amino acids and differ from each other only at an internal exon encoding amino acids 153 through 177, also due to alternative splicing of exons 6a and 6b. The differences in the amino acid sequence encoded by these alternate exons affects the theoretical actin-binding pattern of the tropomyosins, such that TM-5b is expected to bind actin with greater affinity than TM-5a. TM-2 and TM-3 are transcribed from the upstream promoter, and TM-5a and TM-5b are transcribed from an internal promoter. In addition, all four isoforms contain the identical COOH-terminal coding region. RNA protection analyses revealed that the mRNA for each isoform is expressed in a number of different tissues and cell types, although the expression of some isoforms is restricted to particular cell types. Furthermore, the expression of mRNA encoding these isoforms was found to be altered in a number of different virally transformed cell lines. The changes in the expression of tropomyosin mRNAs in transformed cells reflect changes in the relative use of the two promoters, as well as the relative use of alternatively spliced exons 6a and 6b.

Actins↗
PubMed1981

Meniscectomy in children: results in 59 knees.

Forty-nine children undergoing meniscectomy have been reviewed. Fifty-nine knees were examined with a mean follow-up period of 7.5 years. There was an equal number of operations in both sexes, with a high proportion of operations on the lateral meniscus. A good result was noted in 68 per cent of boys and 29 per cent of girls. Only 27 per cent of patients had normal radiographs; 19 per cent had early osteoarthrosis. The preoperative diagnosis was correct in only 65 per cent of cases. It is concluded that meniscectomy is not a benign procedure in children, and that preoperative assessment should include arthroscopy and possibly arthrography.

Adolescent↗
PubMed1978

Difficulties in diagnosing and managing congenital dislocation of the hip.

In a 10-year retrospective study of 25 921 consecutive deliveries in a neonatal unit in Newcastle upon Tyne 271 cases of congenital dislocation of the hips were identified. Of these, the outcome was unsatisfactory in 12: four diagnoses were missed at birth and eight children required further surgical treatment. Radiological abnormalities were detected in a further five children at long-term follow-up examination. From the results of this study and other published series it was concluded that lack of attention to detail was the main cause of inadequate diagnosis and management of congenital dislocation of the hips. More detailed instruction of junior staff, confirmation of the diagnosis by senior staff, the use of a non-removable splint early in treatment, and thorough follow-up by senior staff are all important.

Communication↗
PubMed1977

Psychopathology in children of inpatients with depression: a controlled study.

One quarter of 29 parents hospitalized for depression had children with episodes of depression (eight out of a total of 75 children). None of the children in 41 families with well parents had episodes of depression (a total of 152 children). The differences were significant at the .01 level. It is suggested that symptoms "equivalent" to depression such as hyperactivity, deviant behavior, and learning difficulties are not required in establishing clinical depression in childhood. The methodological shortcomings in this study were discussed.

Adolescent↗
PubMed1971

Two worlds united.

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Community Health Workers↗