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Biomedical subjects

A R Whittemore

Publications and source records attributed to A R Whittemore.

6 recordsLinked to original sources
PubMed1991

Marked cerebrospinal fluid void: indicator of successful shunt in patients with suspected normal-pressure hydrocephalus.

The authors blindly reviewed the charts of 20 patients with normal-pressure hydrocephalus (a disease of unknown cause characterized radiologically as chronic communicating hydrocephalus and clinically by gait apraxia, dementia, and incontinence) who had undergone creation of a ventriculoperitoneal shunt. The initial clinical response to surgery was graded excellent, good, fair, or poor; 5-year follow-up was available in 55% of cases. The magnetic resonance (MR) images obtained in these patients were also blindly reviewed for the magnitude of cerebrospinal fluid (CSF) flow void (graded on the basis of extent rather than degree of signal loss) in the cerebral aqueduct. A significant (P less than .003) correlation existed between good or excellent response to surgery and an increased CSF flow void. The presence of associated deep white matter infarction on MR images did not correlate with a poor response to surgery. On the basis of these findings, it is suggested that patients who fulfill the clinical criteria of NPH and have an increased CSF flow void undergo creation of a shunt.

Aged↗
PubMed1989

Comparison of cocurrent and countercurrent flow-related enhancement in MR imaging.

Patterns of flow-related signal loss and enhancement have been observed in fluid moving perpendicular to the imaging plane on multi-section-acquisition magnetic resonance images. These patterns depend on whether the flow is in the same direction (cocurrent) or opposite (countercurrent) to the direction of sequential section excitation. For a given velocity, flow-related enhancement penetrates deeper into the imaging volume with countercurrent flow than with cocurrent flow. The signal intensity of inner sections is generally greater with countercurrent flow than with cocurrent flow and depends on the velocity. These effects were investigated quantitatively with phantom studies and correlated with theoretical predictions. It was found that the limited penetration of flow-related enhancement with cocurrent flow is a consequence of recently saturated upstream protons flowing into the section to be excited. The flow-related enhancement penetrates farther with countercurrent flow, because inflowing spins have had a greater period of time to recover from the saturating effect of the radio-frequency pulse. Because different laminae have different time intervals to recover magnetization, this also accounts for the observation of concentric rings representing laminar flow in the countercurrent direction.

Image Enhancement↗
PubMed1989

The anatomic basis of vertebrogenic pain and the autonomic syndrome associated with lumbar disk extrusion.

Extruded lumbar intervertebral disks traditionally have been classified as posterior or central in location. A retrospective review of 250 MR imaging examinations of the lumbar spine that used mid- and high-field imagers revealed 145 positive studies, which included a significant number of extrusions extending anteriorly. With the lateral margin of the neural foramen/pedicle as the boundary, 29.2% of peripheral disk extrusions were anterior and 56.4% were posterior. In addition, a prevalence of 14.4% was found for central disk extrusions, in which there was a rupture of disk material into or through the vertebral body itself. The clinical state of neurogenic spinal radiculopathy accompanying posterior disk extrusion has been well defined; however, uncomplicated anterior and central disk extrusions also may be associated with a definite clinical syndrome. The vertebrogenic symptom complex includes (1) local and referred pain and (2) autonomic reflex dysfunction within the lumbosacral zones of Head. Generalized alterations in viscerosomatic tone potentially may also be observed. The anatomic basis for the mediation of clinical signs and symptoms generated within the disk and paradiskal structures rests with afferent sensory fibers from two primary sources: (1) posterolateral neural branches emanating from the ventral ramus of the somatic spinal root and (2) neural rami projecting directly to the paravertebral autonomic neural plexus. Thus, conscious perception and unconscious effects originating in the vertebral column, although complex, have definite pathways represented in this dual peripheral innervation associated with intimately related and/or parallel central ramifications. It is further proposed that the specific clinical manifestations of the autonomic syndrome are mediated predominantly, if not entirely, within the sympathetic nervous system. The directional differentiation of lumbar disk extrusions by MR, together with a clarification and appreciation of the accompanying clinical somatic and autonomic syndromes, should contribute both to understanding the specific causes as well as to establishing the appropriate treatment of acute and chronic signs and symptoms engendered by many nonspecific disease processes involving the spinal column.

Adult↗
PubMedDate not supplied

Association of deep white matter infarction with chronic communicating hydrocephalus: implications regarding the possible origin of normal-pressure hydrocephalus.

The coexistence of cerebrovascular disease leading to deep white matter infarction and normal-pressure hydrocephalus has been noted previously in clinical studies, as both diseases can present with the triad of gait disturbance, dementia, and incontinence. The purpose of this MR study was to determine if the two diseases demonstrated a statistical association. Evidence of patchy periventricular hyperintensity representing presumed deep white matter infarction was sought in 20 patients shunted for normal-pressure hydrocephalus and in 35 additional consecutive patients with clinical symptoms and MR findings consistent with normal-pressure hydrocephalus. Deep white matter infarction was also sought in 62 consecutive age-matched control subjects. There was a statistically significant (p less than .001) higher association (58%) of marked infarction in the 55 patients with normal-pressure hydrocephalus than in the age-matched controls (24%). MR findings of communicating hydrocephalus (ventriculomegaly and increased aqueductal CSF flow void) were sought in 78 consecutive patients with presumed deep white matter infarction, and the degree of severity of the two diseases was also found to be statistically significant (p less than .05). In view of this association, the possibility that the two diseases are related was considered. A potential mechanism is discussed whereby deep white matter infarction leading to decreased periventricular tensile strength could result in communicating hydrocephalus. It is plausible that normal-pressure hydrocephalus may result from a number of different insults to the brain.

Aged↗
PubMedDate not supplied

MR imaging of callosal and corticocallosal dysgenesis.

Callosal dysgenesis implies a malformation of the corpus callosum with origins in the embryogenesis of the telencephalon. A retrospective review of 15 cases of callosal dysgenesis revealed three distinct categories: agenesis (three subjects), hypogenesis (nine subjects), and hypoplasia (three subjects). The basis of this distinction rests upon considerations of neural tube closure, formation and maintenance of the inductive plate of the massa commissuralis, and migration of the neuronal elements of the cerebral cortex responsible for the projection of the commissural fibers of the corpus callosum. These processes are somewhat interdependent in their expression and consequence, resulting in a unique mosaic of callosal and cortical gray matter and hemispheric white matter configurations that have individually varying clinicoradiologic manifestations.

Adult↗