Alexander D. Rae-Grant

Internal carotid artery redundancy is significantly associated with dissection.

Background and Purpose Redundant internal carotid arteries have been considered a risk factor in tonsillectomy, adenoidectomy, and surgical treatment of peritonsillar abscess and also a potentially treatable cause of stroke. However, an association between internal carotid artery redundancy and spontaneous dissection has not yet been clearly demonstrated. Methods We reviewed, for spontaneous carotid artery dissection, records of all patients admitted to our institution during the period from 1986 through 1992 with the diagnosis of stroke or transient ischemic attack. We also reviewed 108 percutaneous cerebral arteriograms performed between September 1992 and December 1992 for presence of carotid artery redundancies. Results Thirteen patients exhibited spontaneous dissection. Of these, 8 of 13 (62%) patients and 13 of 20 (65%) internal carotid arteries, viewed to the siphon, had significant redundancies, kinks, coils, or loops. Of 108 consecutive arteriograms of patients without dissection, in which 187 internal carotid arteries were viewed to the siphon, there were 20 (19%) patients and 22 (12%) of 187 vessels with significant redundancy. Five patients in the dissection group and 2 in the nondissection group had bilateral internal carotid artery redundancy (P=.0019 and P=.0001, respectively). Conclusions We found a significant correlation between internal carotid artery redundancy and dissection, particularly if redundancy is present bilaterally.

Post traumatic extracranial vertebral artery dissection with locked-in syndrome: a case with MRI documentation and unusually favourable outcome.

A patient with a right vertebral artery dissection occurring after minor head trauma progressed to a massive pontine infarction. An unusually favourable outcome and MRI imaging are discussed.

Type III intermittency: a nonlinear dynamic model of EEG burst suppression.

Burst suppression electroencephalograms from 9 comatose patients have been studied using nonlinear dynamic techniques. These EEG records show many dynamical features characteristic of nonlinear systems, including sensitive dependence on initial conditions, self-organization, similarity across scales, and intermittency. Histograms of burst durations showed an asymmetric distribution with a decreasing tail of increasing duration. Interpreting the histograms from the standpoint of intermittency classifications of iterated dynamical maps, the absence of any conspicuous maximal cut-off duration suggests a type III intermittency. The power-law exponent of the decreasing tail is -3/2 for type III intermittency in the large scale sample size limit, and we have found the EEGs to be consistent with type III intermittency behavior. We have also developed a nonlinear algorithm which models burst suppression pattern based on a low dimensional return map. Burst suppression pattern appears to be the constrained activity of a nonlinear dynamical system at the transition to chaos.

Development of a novel EEG rating scale for head injury using dichotomous variables

We developed a new EEG rating scale for electrographic assessment of head injured patients. Phenomena present in posttraumatic EEG were scored as dichotomous variables (present or absent). These phenomena included background activity (alpha, beta, theta, delta), sleep spindles, focal abnormalities, reactivity and variability, epileptiform activity, and specific comatose patterns. Each variable was weighted according to its perceived prognostic value: i.e., normal alpha 10, flat EEG -10, spindles 4, etc. Combinations of possible scores ranged from +23 to -10. Fifty-seven EEGs from different head injured patients were independently and retrospectively analyzed by two investigators. There was a high correlation for intra- (r = 0.95) and inter- (r = 0.85) observer rating using the dichotomous test. When patients with scores over 15 (i.e., with reactive alpha) and patients with scores of -10 (i.e., ECI records) were excluded, the intra-rater and inter-rater correlations were still high (0.81 and 0.76, respectively). There was a high correlation between Glasgow outcome score at discharge and the dichotomous EEG score. This EEG scale scores most major categories of EEG activity, utilizes a multipoint scale for correlation purposes, and allows data to be analyzed in sub-categories (i.e., spindles in coma). The separate weighting score allows for refinement of the scale after data collection (i.e., to fit prospective outcome). We feel that this scale is reproducible and valid, and may be applicable to other patient groups with severely altered EEGs.

Episodic low-amplitude events: an under-recognized phenomenon in clinical electroencephalography.

In a series of 20 EEGs from 15 patients, well-defined brief attenuations occurred interspersed among the background activity. These episodic low-amplitude events (ELAEs) typically lasted 0.5-4 s. They were hemispheric or bisynchronous and occurred in patients with coma of various etiologies, including status epilepticus. The episodes of attenuation were brief and no bursts of activity were present, distinguishing this finding from burst-suppression. Prognosis was poor in the patients with coma due to entities other than status epilepticus. In the setting of status epilepticus, the prognosis depended on the etiology. This pattern may be an ictal phenomenon, or a product of waveform simplification. ELAEs are a manifestation of seriously abnormal EEG activity and correlate with a 50% mortality.

Alzheimer's disease in Down's syndrome with SPECT.

Alzheimers disease often occurs in patients with Downs syndrome. SPECT scanning with I-123 IMP and Tc-99m HMPAO identifies decreased cerebral perfusion and metabolism in these patients at lower cost. In this case, SPECT scanning revealed changes in Alzheimers disease in a Downs syndrome patient.

Episodic Low Amplitude Events.

ABSTRACT.In a series of 27 electroencephalograms from 22 patients, well-defined brief attenuations occurred interspersed among the background activity. These “episodic low amplitude events” (ELAEs) typically lasted 0.5–4 seconds. They were hemispheric or bisynchronous and occurred in patients with coma of various etiologies, including status epilepticus. The episodes of attenuation were brief and no bursts of activity were present, distinguishing this finding from burst-suppression. In the patients with coma other than status epilepticus, prognosis was poor. In the setting of status epilepticus, the prognosis depended on the etiology of status. ELAEs are a manifestation of seriously abnormal electroencephalographic activity and correlate with α 45% mortality.

A private practice model for teaching and research activities

The majority of neurologists in the United States are in fee for service patient management, dividing their time between hospital and office based practice. Many have had subspecialty training or have had research experience. It is our belief that research should be a component of a neurologists practice. This is particularly true for an assessment of outcome. In order to accomplish this, we have developed a system which includes patient management, teaching, and clinical research, within our fee for service model.