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Biomedical subjects

L P Mark

Publications and source records attributed to L P Mark.

At least 19 recordsLinked to original sources
PubMed2002

Single photon emission computerized tomography (SPECT) in detecting neurodegeneration in Huntington's disease.

Single photon emission computerized tomography (SPECT) studies were performed on 34 manifest Huntington's disease (HD) patients at various stages of clinical pathology ranging from early chorea to late dystonia with or without signs of dementia and 12 pre-symptomatic patients with abnormal terminal CAG expansions. Thirty HD patients with obvious clinical signs and seven pre-symptomatic patients without signs or symptoms of HD displayed selective caudate hypoperfusion by direct visual inspection. Such qualitative, selective striatal hypoperfusion patterns can be indicative of early and persistent metabolic changes in striatal neuropathology. SPECT studies can be useful in documenting early pre-clinical changes in patients with abnormal terminal CAG expansions and in confirming the presence of caudate pathology in patients with clinical signs of HD.

Adult↗
PubMed2000

Rosai-Dorman disease causing cervical myelopathy.

STUDY DESIGN: A case report of a rare disease entity and review of the literature. OBJECTIVES: To illustrate the occurrence of an unusual disease affecting the spine and spinal canal. SUMMARY OF BACKGROUND DATA: Rosai-Dorman disease is considered an idiopathic benign lymphoproliferative disease that typically occurs in the earlier decades of life. The usual manifestation is painless massive cervical lymphadenopathy, although involvement of many extra nodal sites is common. This case illustrates Rosai-Dorman disease occurring in an elderly man with myelopathy and mass lesions of the cervical, thoracic, and lumbar spinal canal without typical lymphadenopathy.- METHODS: Case report illustrating clinical presentation as well as radiographic and pathologic findings, including comparisons to cases previously reported. RESULTS: Surgical decompression with incomplete resection of the lesion was performed, providing diagnosis and treatment guidance. The patient experienced significant neurologic improvement of myelopathy. CONCLUSIONS: Recognizing clinical and laboratory features of this disease may permit earlier diagnosis and limit or avoid surgical intervention in some cases.

Aged↗
PubMed2000

Spin-lock magnetic resonance imaging of muscle in patients with autosomal recessive limb girdle muscular dystrophy.

Spin-lock imaging is a new magnetic resonance imaging (MRI) technique used to reflect the microstructural integrity of muscle. The purpose of this study was to characterize spin-lock contrast (SLC) of calf muscles in limb girdle muscular dystrophy (LGMD). The calf muscles of 5 patients with LGMD and 10 healthy volunteers were imaged with an off-resonance magnetic resonance (MR) spin-lock suppression pulse. Spin-lock suppression ratios were calculated for anterior tibialis, posterior tibialis, soleus, and gastrocnemius muscles. Clinical assessments of muscle strength were compared to the spin-lock suppression ratios in the LGMD group. Strong SLC was observed in healthy muscles, with mean (+/- SD) suppression ratios ranging from 51.2% (+/- 3.6%) to 56.3% (+/- 1.3%). In diseased muscle, spin-lock signal suppression was reduced by 8%-70%, demonstrating an inverse correlation between symptom duration and suppression ratios. Spin-lock contrast in the patients with LGMD, as a reflection of tissue integrity, was best preserved in posterior tibialis, anterior tibialis, soleus, and gastrocnemius muscles in descending order. Clinical assessments did a poorer job of differentiating than SLC did and were in poor agreement with spin-lock suppression ratios. Spin-lock MRI can quantify microstructural changes in LGMD and appears to provide information not obtainable from clinical evaluations. This suggests that this noninvasive technique may be useful in evaluating the extent, progression, and response to therapy of LGMD.

Adolescent↗
PubMed2000

Too many treatments for Parkinson's disease: how should they be used?

Surgical ablation for Parkinson's disease was abandoned in the 1970s after successful clinical trials of L-DOPA and L-DOPA/decarboxylase inhibitor combinations and early dopamine receptor agonists were added to prolong a viable therapeutic window beyond 5 years. The development of newer agonists with variations in receptor subtype specificity and new enzyme inhibitors with combinations of central and peripheral effects have continued to attract attention as therapeutic alternatives. Treatment options are now coming full circle with a rebirth of stereotactic neurosurgical alternatives to a wide variety of pharmacologic paradigms. The authors propose a rationale for selecting differing treatment options within historical perspective and modern treatment goals using both medical and surgical alternatives.

Antiparkinson Agents↗
PubMed1998

Understanding the brain stem.

This article highlights features of brain anatomy that are important to know in interpreting magnetic resonance images. This article concentrates on the names of some brain stem structures, the three-dimensional appearance of six important tracts, and the location of cranial nerve nuclei.

Brain Stem↗
PubMed1998

Near-resonance saturation pulse imaging of the extraocular muscles in thyroid-related ophthalmopathy.

PURPOSE: We examined the utility of near-resonance saturation pulse imaging (magnetization transfer [MT] and spin lock) in characterizing microstructural changes occurring in the extraocular muscles of patients with thyroid-related ophthalmopathy (TRO). METHODS: Eight healthy volunteers and 10 patients with TRO were imaged using an off-resonance saturation pulse in conjunction with conventional spin-echo T1-weighted imaging at frequency offsets of 500, 1000, 1500, and 2000 Hz from water resonance. The relative contributions of MT and spin-lock excitation to image contrast at each frequency offset were estimated using a computer simulation model. Suppression ratios were calculated for the control and TRO groups from measurements obtained on two successive coronal sections in the widest portion of the inferior and medial rectus muscles bilaterally. A repeated measures analysis of variance and a parametric correlation analysis were performed to evaluate maximum cross-sectional area, MR-generated signal, and suppression ratios for the extraocular muscles examined. RESULTS: Our computer model suggested that saturation of extraocular muscles was due to pure MT effects with our off-resonance pulse at 2000 and 1500 Hz, to a combination of MT and spin lock at 1000 Hz frequency offset, and, primarily, to spin-lock excitation at 500 Hz frequency offset. Suppression ratios for the extraocular muscles of the TRO patients were significantly lower than that observed for the control subjects at 1500, 1000, and 500 Hz frequency offset. This differential saturation effect was maximal at 500 Hz frequency offset, with mean suppression ratios for the inferior and medial rectus muscles of 27% for the healthy subjects and 20% for the TRO group. CONCLUSION: Both MT and spin-lock contrast of the extraocular muscles in patients with TRO differ significantly from that observed in control subjects. Near-resonance saturation pulse imaging may enhance our understanding of the microstructural changes occurring in the extraocular muscles of these patients.

Adult↗
PubMed1997

MR imaging of lumbar spondylolysis: the importance of ancillary observations.

OBJECTIVE: The purpose of this study was to determine the frequency of characteristic ancillary MR findings in patients with lumbar spondylolysis. MATERIALS AND METHODS: The radiology reports and clinical records of 64 patients (16 female, 48 male; 12-77 years old) with 66 levels of lumbar spondylolysis who had undergone MR imaging were retrospectively reviewed. Spondylolysis was established by conventional radiography in all 64 patients and by CT in 18 patients. The proportion of patients with spondylolysis in whom sagittal MR images showed ancillary findings of an increased sagittal diameter of the spinal canal, reactive marrow changes in the pedicle, or abnormal wedging of the posterior aspect of the vertebral body was retrospectively determined. This proportion was then compared with the proportion of patients in whom spondylolysis was correctly diagnosed by the initial interpreters of the MR images, who used only direct visualization of defects of the pars interarticularis to make the diagnosis. RESULTS: Twenty (30%) of 66 levels of lumbar spondylolysis were misdiagnosed when the MR images were initially interpreted using direct visualization of defects of the pars interarticularis. An increased sagittal diameter of the spinal canal was the most common ancillary observation, occurring at 60 of 66 levels of lumbar spondylolysis. This finding was present in all patients with grade II, III, or IV spondylolisthesis, in 95% of patients with grade I spondylolisthesis; and in 77% of patients with no anterolisthesis. Thirty-two (48%) of 66 lumbar levels showed wedging of the posterior aspect of the vertebral body, which correlated significantly with the grade of spondylolisthesis. Reactive marrow changes in the pedicle distinct from normal adjacent levels were seen on MR images in 24(36%) of 66 levels of lumbar spondylolysis. On MR images, 97% of all levels of lumbar spondylolysis yielded one or more ancillary observations, including all 20 of the cases originally misdiagnosed. CONCLUSION: The combined use of ancillary observations and direct visualization of pars interarticularis defects makes MR imaging effective in revealing lumbar spondylolysis.

Adolescent↗
PubMed1997

Anatomic relationship of the oculomotor nuclear complex and medial longitudinal fasciculus in the midbrain.

PURPOSE: To compare the MR characteristics of the oculomotor nucleus with its appearance on anatomic images. METHODS: Specimens of cadaveric brains were imaged in a 3.0-T MR imager equipped with a 3.0-cm solenoid coil. The specimens were sectioned, stained, and examined histologically. On anatomic sections, the oculomotor nuclei, medial longitudinal fasciculus, red nuclei, and oculomotor nerve were identified. The MR images were then compared with the anatomic sections. RESULTS: The oculomotor nuclei, medial longitudinal fasciculus, red nuclei, and oculomotor nerve could be identified on MR images by their size, shape, signal intensity, and location. CONCLUSION: MR images show the anatomic relationship of the oculomotor nerve complex, medial longitudinal fasciculus, and related structures in the brain stem.

Abducens Nerve↗
PubMed1997

Recent advances in MR spectroscopy expand its applications in neurologic disease.

MRS extends the diagnostic power of MRI by displaying the biochemical composition of a selected tissue or region. When MR imaging shows a lesion, the evaluation of the chemical composition by MRS can help determine whether biopsy, observation or medical treatment is indicated. It can save some patients from biopsy prior to radiation or chemotherapy. In the future, both the image information and the spatial distribution of chemical constituents throughout the brain will be displayed with techniques such as chemical shift imaging (CSI). MRS improves the accuracy of MRI diagnosis and prognosis. MRS is performed at many sites in the country and is reimbursed by many insurers. MRS has been approved by the AMA for a CPT-4 code for reimbursement.

Adult↗
PubMed1996

MR appearance of the internal architecture of Ammon's horn.

PURPOSE: To determine whether the four subdivisions of Ammon's horn and six layers of CA1 seen histologically can be demonstrated with MR imaging. METHODS: Specimens of cadaver brains were imaged in a 3.0-T MR imager with a 3.0-cm solenoid coil. The specimens were sectioned, stained, and examined histologically. On anatomic sections, the four subdivisions of Ammon's horn and six layers of CA1 were identified. The MR images were then compared with the anatomic sections. RESULTS: Using geographic characteristics, we identified the four subdivisions of Ammon's horn. In CA1, the six layers could be identified by variations in signal intensity, width, and location. CONCLUSION: This study suggests that, with MR imaging of sufficiently high resolution, the internal architecture of Ammon's horn may be identified.

Brain Mapping↗
PubMed1994

Lacrimal collecting system lymphomas: integration of magnetic resonance imaging and therapeutic irradiation.

Lymphomas arising within the lacrimal collecting system are rare tumours and unusual causes of lacrimal obstructive symptoms. The presentation, diagnosis, and treatment of this disease in five patients are described, as well as a review of the existing literature. Emphasized in this series is the efficacy of magnetic resonance imaging of these presentations and the importance of irradiation in their treatment.

Adult↗
PubMed1994

Imaging white matter tracts and nuclei of the hypothalamus: an MR-anatomic comparative study.

PURPOSE: To evaluate the MR appearance of the hypothalamus and its associated white matter tracts. METHODS: Coronal and sagittal spin-echo images were obtained in cadaver brains. Gross and histologic sections were made of the cadaver brains. The size, shape, signal intensity, course, and pattern of structures in the hypothalamic region were identified in MR images by comparison with the anatomic sections. RESULTS: The mamillary bodies, paraventricular zone of hypothalamic nuclei, postcommissural fornix, mammillothalamic fasciculus, and anterior commissure were identified on the MR images. CONCLUSION: This study suggests that, with MR imaging of sufficiently high resolution, some of the tracts and nuclei in the hypothalamus may be identified.

Humans↗
PubMed1992

Visualization of the distal intratemporal facial nerve with MR imaging: use of an oblique plane.

Although magnetic resonance (MR) imaging routinely is used to evaluate the facial nerve, the conventional axial, coronal, and sagittal planes are not optimal for demonstrating the tympanic and mastoid portions of the nerve. A vertical oblique plane for MR imaging of these portions of the facial nerve was evaluated. With this plane, the course of the nerve was effectively demonstrated on MR images and corresponding cryosections. The oblique plane can be used to supplant or supplement conventional planes in imaging of the facial nerve.

Facial Nerve↗