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Biomedical subjects

J L Stone

Publications and source records attributed to J L Stone.

At least 109 records · Page 6Linked to original sources
PubMed1988

Multiple intracranial aneurysms: magnetic resonance imaging for determination of the site of rupture. Report of a case.

In a patient with multiple intracranial aneurysms, the clinical examination, computed tomographic brain scan, and cerebral angiogram failed to disclose which of five aneurysms had ruptured. Magnetic resonance imaging (MRI) revealed high signal intensity compatible with hemorrhage in the lower portion of one cerebellar tonsil, and a corresponding posterior inferior cerebellar artery aneurysm was successfully obliterated. We would add MRI to the list of useful adjuncts in identifying which of multiple aneurysms bled.

Female↗
PubMed1987

Nonmelanoma skin cancer in Japanese residents of Kauai, Hawaii.

A prospective 3-year survey of nonmelanoma skin cancer in Japanese-American residents of the Hawaiian island of Kauai was conducted beginning in January 1983. The crude rate for basal cell and squamous cell carcinoma was 123/100,000, 88 times higher than the corresponding figure from Japan. This discrepancy may be attributed to an increase in ultraviolet exposure due to lifestyle and latitude, but arsenic exposure may also have played a role. Nonmelanoma skin cancer in Japanese in Hawaii appears to be a significant problem that has not been appreciated because these malignancies are not reportable to tumor registries.

Aged↗
PubMed1987

Usefulness of different stimuli in visual evoked potentials.

The goal of this study was to determine the relative usefulness of the flash (FL), pattern reversal (PR) of 56', and PR of 28' in 62 patients (pts) with either MS (34) or non-MS (28) compared with normals (19). An abnormal visual evoked potential was found in 58%, 69%, and 81% of the eyes tested in possible, probable, and definite MS and in 88% of the non-MS group. The 28' PR produced the most abnormal responses, the greatest number with either greater than 3 standard deviations (SD) from the mean or greater than 2 SD in both MS and non-MS groups. The FL was second best at producing the most abnormal responses, but more often produced the only abnormality (29), compared with 28' PR (11). The 56' PR produced the only abnormality in none of the MS pts and in only one of the non-MS pts. In all categories (most abnormal, greater than 3 SD, greater than 2 SD, the only abnormality of greater than 3 SD or greater than 2 SD, and other peaks abnormal), the 28' PR was usually by far the best stimulus for definite (and probable) MS, but equally as effective was the FL in the possible MS pts Our data suggest the usefulness of 28' and not 56' PR, but the FL is especially useful in pts with possible MS.

Adolescent↗
PubMed1987

Modified auditory brainstem responses (MABR): Part I--Rationale and normative study.

Binaural, rapid rate, ABR stimulation at four intensity levels (MABR) as well as ABR at two intensity levels were carried out in 35 normal subjects. Latency and amplitude relationship with stimulus intensity of wave V of the MABR was extensively studied in these subjects. MABR recording is a rapid, sensitive, non-invasive screening method readily done at the intensive care bedside. Less than 10 minutes is required in addition to the ABR examination time. Normality of the MABR potentials implies a high degree of peripheral auditory and brainstem functional integrity, augmenting information gained with standard ABR technique. Only clinical trials can decide if MABR sensitivity will exceed that of the ABR and prove helpful to diagnosis and patient care.

Acoustic Stimulation↗
PubMed1986

Electrocochleography recorded non-invasively from the external ear.

A method is described to record cochlear evoked potentials in humans (ECochG) with a low impedance electrode on the external ear near the opening of the external auditory canal. A piezoelectric click stimulus was delivered to the ear through a polyethylene tube creating diminution of stimulus artifact and a signal delay. Wave forms resembling the cochlear microphonic (CM), summating potential (SP) and the eighth nerve action potential (N1) were differentially accentuated by changes in stimulation and recording parameters. The addition or subtraction of condensation and rarefaction click wave forms further clarified the N1 and SP, or the CM potential, respectively. These responses can be recorded with most contemporary evoked response equipment. This non-invasive method of ECochG lends itself well to the study of hearing loss and possibly other neurologic disorders, and may complement BAER examination especially when wave I is poorly delineated.

Audiometry, Evoked Response↗
PubMed1986

Acute subdural hematoma: direct admission to a trauma center yields improved results.

We studied 128 patients admitted over a 12 1/2-year period to the Cook County Hospital Trauma Unit with acute subdural hematoma (ASDH): 82 were admitted directly and 46 were admitted after transfer from another hospital; 59% of the entire group died and only 27% obtained a functional recovery. As a group, the transferred patients, who suffered delays of several hours before receiving definitive surgical care, fared significantly worse than the patients with equivalent trauma who were admitted directly. The mortality of the transferred patients was 76%, compared to 50% of the direct admit patients. The outcome was also worse for transfer patients who experienced a 'lucid interval' or with alcohol intoxication. We conclude that the delays associated with failure to admit patients with ASDH directly to a head trauma center cause an excessive mortality and morbidity which could potentially be avoided by proper triage.

Adolescent↗
PubMed1986

Neuroradiological and electroencephalographic features in a case of temporal lobe status epilepticus.

A patient with medically intractable status epilepticus of temporal lobe origin is presented. A computed tomogram showed a low density area adjacent to the midbrain, possibly related to atrophy of the medial temporal lobe. Cerebral angiography revealed early filling veins and an anterior temporal blush. Magnetic resonance (MR) scanning (T2 weighted images) showed increased signal intensity in the region of the amygdala and anterolateral left temporal lobe. Ictal activity was recorded from scalp electrodes over the left temporal area, and many paroxysms were recorded from cortical surface electrodes. An anterior temporal lobectomy revealed only gliosis. The cerebral blood flow changes accompanying status epilepticus of focal origin are reviewed, and a possible relation of electroencephalographic, angiographic, and MR findings is discussed.

Adult↗
PubMed1985

Tensile strength of bovine trabecular bone.

Data on the tensile and compressive properties of trabecular bone are needed to define input parameters and failure criteria for modeling total joint replacements. To help resolve differences in reports comparing tensile and compressive properties of trabecular bone, we have developed new methods, based on porous foam technology, for tensile testing of fresh/frozen trabecular bone specimens. Using bovine trabecular bone from an isotropic region from the proximal humerus as a model material, we measured ultimate strengths in tension and compression for two groups of 24 specimens each. The average ultimate strength in tension was 7.6 +/- 2.2 (95% C.I.) MPa and in compression was 12.4 +/- 3.2 MPa. This difference was statistically significant (p = 0.013) and was not related to density differences between the test groups (p = 0.28). Strength was related by a power-law function of the local apparent density, but, even accounting for density influences, isotropic bovine trabecular bone exhibits significantly lower strengths in tension than in compression.

Animals↗
PubMed1985

W. W. Keen: America's pioneer neurological surgeon.

The contributions of William Williams Keen to the development of neurological surgery were greater than those of any other American surgeon in the last quarter of the 19th century. His close association with S. Weir Mitchell, the father of American neurology, spanned more than 50 years. Keen's early publications included topics of neuroanatomical and neurophysiological interest. He was the first surgeon in America to remove a meningeal tumor and effect a cure and the first in America to stimulate the brain at operation. He made contributions to the surgical treatment of hydrocephalus, craniostenosis, torticollis, trigeminal neuralgia, and nervous system trauma. Keen's surgical texts provided an important foundation for Cushing, Frazier, and those that followed. Showered with honors as America's dean of surgery, Keen lived to see the many specialties evolve.

History, 19th Century↗
PubMed1985

The relationship between visual seizures and visual evoked potentials.

We have studied a patient (pt) in status epilepticus with visual seizures (szs) arising focally from the right occipital area and have recorded the visual evoked potential (VEP) to three different stimuli under three different conditions (during, between and with no szs). The pt experienced "sparkling" in the contralateral visual field as the sz and the intensity of the "sparkling" was directly related to the frequency of the ictal activity recorded on the EEG. During the szs the VEPs could still be recorded, but the amplitude of the P100 was higher on the contralateral side with pattern reversal (PR) stimuli, and with flashes (FL) the positive peak after the P100 was less evident on the ipsilateral side. Latencies to these latter two positivities were generally shorter than in normals, with much greater standard deviations ipsilaterally with FL and contralaterally with PR, especially during the actual szs. The relationship between VEP generation and visual sz phenomena is discussed.

Adult↗
PubMed1984

Force ratios in the quadriceps tendon and ligamentum patellae.

We measured forces in the quadriceps tendon and ligamentum patellae in six human cadaver knee joints loaded through a range of flexion angles from 30 to 120 degrees. Using standardized loads based on one-sixth of maximum isometric quadriceps moments reported in human volunteers, we measured maximum average forces at 60 degrees flexion of 532 N in the quadriceps tendon (FQ) and 470 N in the ligamentum patellae (FL). Linear extrapolation to full maximum extensor moments results in estimates of 3,200 N for FQ and 2,800 N for FL. The force ratio (FL/FQ) reached a maximum value of 1.27 at 30 degrees and minimums of 0.7 at 90 and 120 degrees knee flexion. Contrary to prevailing opinion, our results indicate that the patella is not a simple pulley that serves only to change the direction of equal forces in the quadriceps tendon and ligamentum patellae. Instead, the ratio of forces in these structures varies significantly with flexion angle. The ratio appears to be determined by the changing location of the patellofemoral contact area relative to the insertions of the tendon and ligament. These findings emphasize the biomechanical importance of patellar length and of the vertical dimensions and locations of the patellofemoral contact area. Attempts at surgical intervention for the treatment of disorders of the extensor apparatus should recognize these variations. Procedures that tend to move the contact area more proximally (at a particular flexion angle) will also tend to decrease the FL/FQ ratio.

Aged↗
PubMed1983

Multiaxial strength characteristics of trabecular bone.

Bovine trabecular bone specimens were tested in multiaxial stress, including pure shear, in a special test device. Shear strength was proportional to apparent density to the exponent 1.65, in approximate agreement with theoretical and experimental studies on the shear strengths of porous foams. The mean shear strength was 6.60 +/- 1.66 MPa, after normalizing for apparent density. This compares well with normalized shear strengths from Saha and Gorman's (1981) study on human femora. A scanning electron microscope study indicated random trabecular architecture and a complex fracture mechanism at the level of the individual trabecular struts. Hoffmann's (1967) 3-D isotropic failure criterion was applied to the multiaxial test data, along with data from uniaxial compression tests, indicating a compressive strength approximately three times the tensile strength.

Animals↗
PubMed1983

Clinical and electrophysiologic recovery in Arnold-Chiari malformation.

The case of a 16-year-old boy with occipital headache, diplopia, ataxia, and weakness in the lower extremities of 1-month duration is reported. Slowness of mentation, speech, and motor action was also present. Massive chronic hydrocephalus was indicated by an enlarged head. The prominent clinical features suggested involvement of the brainstem, and contrast studies showed compression of the brainstem and a filling defect posteriorly at C1-2. Brainstem auditory evoked potential latency suggested bilateral lesions of the brainstem. Posterior fossa decompression confirmed the presence of an Arnold-Chiari malformation, with the cerebellar tonsils as low as C-3. The fourth ventricle was microdissected and opened. Remarkable clinical and evoked potential recovery ensued over several months. Clinical-anatomic and anatomic-physiologic correlations in Arnold-Chiari malformation are discussed.

Adolescent↗