Gale R. Ramsby

Brain morphometric analysis in achondroplasia

Article abstract-Rationale and objectives: We undertook an MRI brain morphometric analysis to investigate the relationships between brain and skull base growth and clinical function in patients with achondroplasia as compared to normal controls. Methods: Patients selected for evaluation included pediatric patients who underwent T1 and T2 or dual-echo, proton-density axial T1- and T2-weighted and T1 sagittal brain MRI during 1988 to 1992. Study subjects (n = 11) were diagnosed with achondroplasia by clinical and radiologic criteria and compared to an age- and gender-matched control group (n = 25). Twenty-four predetermined ventricular and brain parenchymal dimensions and area calculations were evaluated. Data were analyzed using two-tailed t tests, chi-squared analysis, ANOVA, and ANCOVA, adjusting for age and sex. Correlational analyses with respect to subject type and age were done separately. Results: There were 36 patients (11 subjects with 15 MRI examinations, mean age 2.3 years, and 25 controls with 26 MRI examinations, mean age 3.0 years). Significant differences existed for 11/17 measures. Achondroplasts had a significantly larger bifrontal width (p < 0.0001), bicaudate width (p < 0.0001), frontal horn diagonal length (p < 0.05), biatrial width (p < 0.0001), biparietal diameter (p < 0.05), and iter to incisural line distance (p < 0.0001). Achondroplasts had significantly smaller frontal lobe depths (p < 0.01), optic tract angles (p < 0.0001), foramen magnum diameters (p < 0.0001), and sinojugular transition zones (p < 0.05). There were no differences in brainstem heights or fourth ventricular widths between achondroplasts and controls. Furthermore, with respect to age, frontal lobe depth was smaller when compared to controls and the descending sigmoid sinus area became increasingly larger. Conclusions: Achondroplastic subjects experience dynamic changes in brain morphometry resulting in a rostral displacement of the brainstem with gradual compression of the frontal lobes due to enlargement of the supratentorial ventricular spaces commensurate with an increase in venous sinus distension. NEUROLOGY 1995;45: 519-524

Portacaval Anastomosis and Peptic Ulcer: A Nonassociation

The incidence of peptic ulcer is increased in cirrhosis and is widely believed to be even greater in cirrhotic patients with portacaval anastomosis (PCA). Two prospective, controlled investigations of prophylactic PCA were evaluated to compare the frequency of peptic ulcer in two groups of cirrhotic patients with similar clinical and laboratory manifestations of cirrhosis randomly selected to be an unoperated Control Group (60 patients) or to have PCA (Shunt Group, 48 patients). In addition, nonrandomized groups of cirrhotic patients, 77 of whom were excluded from the randomized study and 44 of whom had therapeutic PCA, were studied. A diagnosis of chronic peptic ulcer was based on the demonstration of an ulcer crater by X-ray, endoscopy, surgery, or autopsy. Prior to inclusion in these studies, approximately 10% of patients had had peptic ulcer. After inclusion, during a mean follow-up period of 45 months, 12% of both the Control and Shunt Groups developed peptic ulcers. The frequency of complications of peptic ulcer, of recurrence of peptic ulcer, or of acute or symptomatic (unproved) ulcer were similar in both groups. Ulcers tended to develop later in shunted than in unshunted patients. Similar data were obtained from three of four other controlled investigations of PCA. This investigation does not find an increased occurrence of peptic ulcer after PCA. The frequency of ulcer in cirrhosis appears to increase with the duration of the disease independent of the presence or absence of PCA.

Familial band heterotopias simulating tuberous sclerosis

We report the clinical and neuroimaging findings of a mother and daughter with seizure disorders and band heterotopias seen on magnetic resonance imaging studies. These clinicoradiologic findings simulate those for a diagnosis of tuberous sclerosis complex. Clinicians should be aware of this migrational anomaly and its neuroimaging characteristics, as well as the potential for this specific migrational anomaly to be genetically transmitted.

Accelerated Hypertension With Encephalopathy Due to an Isolated Dissection of a Renal Artery Branch Vessel

Typical causes of renovascular hypertension include intramural atherosclerotic lesions of the main renal arteries or their branches and fibromuscular dysplasia of the renal arterial wall with luminal narrowing. We report a patient with new-onset, accelerated hypertension (blood pressure 220/140 mm Hg, status epilepticus, retinal hemorrhages) secondary to a dissection of the anterior division of the right renal artery that was accompanied by hyperreninemia, hyperaldosteronism, and hypokalemia. At presentation in the untreated state, unstimulated plasma renin activity and the serum aldosterone level were markedly elevated. Following right nephrectomy, blood pressure levels normalized without antihypertensive therapy, and plasma renin activity, serum aldosterone and potassium levels normalized. Histologic study of the right renal artery showed an isolated dissection of the anterior branch of the vessel between the muscularis and adventitia that created marked reduction in luminal diameter and renal ischemia. There was no evidence of any other vascular abnormalities, atherosclerosis, or fibromuscular dysplasia. These findings demonstrate that an isolated dissection of a branch of the renal artery may induce profound hyperreninemia and represents a rare, reversible etiology for accelerated hypertension associated with acute encephalopathy.

Human gallbladder morphology after gallstone dissolution with methyl tert-butyl ether

The effects of methyl tert-butyl ether exposure on the human gallbladder in five patients who were treated for gallstones by contact dissolution is described. Two patients underwent cholecystectomy within 1 week of methyl tert-butyl ether treatment, one patient 2 weeks after, another 10 weeks after, and one 12 weeks after. Indications for cholecystectomy were bilirubinate stones (resistant to methyl tert-butyl ether), catheter dislodgement, bile leakage, and gallstone recurrence (2 patients). Gallstones were dissolved completely in three patients, there was approximately 50% stone reduction in one patient, and no dissolution occurred in the fifth patient. Each gallbladder was examined grossly and histologically. Electron microscopic evaluation was performed in one cases. Typical inflammatory findings of chronic cholecystitis were observed in each gallbladder and were most conspicuous in the submucosa; the mucosal and serosal surfaces were intact. Mild acute inflammatory changes were noted in the submucosa in the two patients with the shortest interval between methyl tert-butyl ether administration and cholecystectomy. There were no ulcerations in the mucosa and no unusual wall thickening or fibrosis in any patient. These observations support the safety of methyl tert-butyl ether perfusion in the human gallbladder; the mild acute changes may be a transient and reversible phenomenon.

Early carcinoma of the gallbladder diagnosed by percutaneous cholecystoscopy

Carc inoma of the ga l lb ladder is an u n c o m m o n mal ignancy t h a t ha s a s t rong associa t ion wi th cholelithiasis. 1 The major i ty of pa t i en t s wi th ga l lb ladder cancer p re sen t wi th s y m p t o m s caused by advanced, incurable disease. 2, 3 Pa t i en t s wi th ear ly and potent ial ly cura t ive t u m o r s a re usua l ly discovered to have ga l lb ladder cancer incidenta l ly a f te r cholecys tec tomy for s y m p t o m a t i c cholelithiasis. 4, 5 Nonopera t ive techniques for t r e a t i ng symptoma t i c gal ls tones a re safe and effective a l t e rna t ives to cholecys tec tomy in those who are poor opera t ive r isks and in pa t i en t s who wish to avoid genera l anes the s i a or the loss of t he i r gal lbladder . 6-9 A cri t ic ism of nonopera t ive t r e a t m e n t s is t h a t t he re will be a smal l n u m b e r of pa t i en t s wi th early, unsuspec t ed ga l lb ladder cancer who will not have potent ia l ly cura t ive t r e a t m e n t of th is ma l ignancy by cholecystectomy. We rou t ine ly pe r fo rm pe rcu taneous cholecystoscopy in pa t i en t s t r e a t ed for s y m p t o m a t i c cholel i thiasis wi th percu ta neous contact dissolut ion or stone extract ion. 7, 10, 11 Pe rcu taneous cholecystoscopy is ut i l ized to ensu re t h a t all ga l ls tones and debris have been to ta l ly removed and to eva lua te the ga l lb ladder mucosa for inc idental t u m o r s or ulcers. In th is repor t we p re sen t a pa t i en t who was found to have an o therwise unsus pected ear ly ca rc inoma of the ga l lb ladder by cholecystoscopy following pe rcu t aneous topical gal ls tone dissolution.

Unsupervised classification of multiecho magnetic resonance images of the pediatric brain with implicit spatial and statistical hypotheses validation

We describe an image segmentation method applied to multi-echo MR images which is unsupervised in that the analyst need not specify prototypical tissue signatures to guide the segmentation. It is well known that different tissue types may be distinguished by their signatures in NMR parameter space (spin density and relaxation parameters T1 and T2). Also, normal tissue may be differentiated from abnormal by means of these signatures. Even though pixel intensity is proportional to weighted mixtures of these parameters in real images several researchers feel there is potential for better segmentation results by processing dual-echo images. These images are inherently registered and require no additional time to acquire the image for the second echo. Our segmentation procedure is a multi-step process in which tissue class mean vectors and covariance matrices are first determined by a clustering technique. The goal here is to achieve an intermediate segmentation which may be subject to quantitative validation.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Automatic development of physical-based models of organ systems from magnetic resonance imagery

The essential goal of this work described herein is to provide a biophysical model within which the effects of the alteration of a variety of geometrical or physical variables within the CSF system can be explored. Our ultimate goal is to be able to divorce such models from the constraints of the artificial geometries (e.g., generalized cylinders) so typical of the usual biophysical model, and to this end we have determined that each structure to be modelled be developed from an actual in-vivo example of the structure, determined by extraction from CT or MR imagery. Onto such models we will then overlay a biophysical structure which will permit us to simulate a variety of different conditions and thereby determine (up to model accuracy) how the simulated condition might in fact impact the in vivo structure were it to be faced with a similar set of physical conditions.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Determination of ventricular structure from multisignature MR images of the brain

The derivation of ventricular structures from a pediatric population is discussed. The original dataset is classified via a metric-based clustering algorithm which is tuned to the signature distribution from the magnetic resonance images (MRIs). The cluster set (or sets) interpreted as cerebrospinal fluid are aggregated throughout the dataset into a group of connected components whose topology is understood. This typically recursive procedure is replaced by a divide-and-conquer approach which substantially reduces the stack space needed for the aggregation. Other class sets can be equivalently aggregated. Visualization and geometry are then simply deduced from the aggregated cluster sets in the data. It is demonstrated how this hierarchical cluster/classification strategy can successfully demonstrate ventricular structure from multisignature MRIs.<<ETX>>

Computation of Tumor Burden in the Pediatric Patient

The application of morphometry (i.e., the construction of volume, area and shape) to neurological disease is not uncommon, and with the advent of Magnetic Resonance Imaging (MRI), the role of computer-assisted morphometry has grown[1,2,3,4]. Typically, a sequence of MR images is taken through a region of interest (ROI) and those pixels which belong to the structure or system under measurement are identified (segmented) within the image. Since the pixel-to-real-geometry conversion factors are known (i.e., voxel dimension in mm 3 is known), simple sums of pixels give rise to volumes and/or areas. These techniques tend to be manual (or semi-automated at best), since the primary difficulty in this procedure is the attachement of labels to image pixels i.e., the association of pixels to known anatomic structures. Some techniques make use of multiple echoes in MRI to employ cluster/classification strategies[2,3,5,6,7], but again the bulk of these necessitate some form of human interaction in the segmentation process. This paper describes the strategy we are pursuing to eliminate human intervention by employing a mixed cluster-topological approach to direct morphometry.