Robert A. Zimmerman

Bone Formation and Inflammation in Cardiac Valves

BackgroundFor nearly a century, the mechanical failure of calcified heart valves was attributed to a passive degenerative process. Recently, several case reports described bone formation in surgically excised heart valves and suggested an unexpected process of tissue repair. Methods and ResultsWe studied the prevalence and pathology of heterotopic ossification in 347 surgically excised heart valves (256 aortic, 91 mitral) in 324 consecutive patients (182 men, 142 women; mean age 68 years) who underwent cardiac valve replacement surgery between 1994 and 1998. The valves were examined microscopically to determine the prevalence and features of bone formation and remodeling. Two hundred eighty-eight valves (83%) had dystrophic calcification. Mature lamellar bone with hematopoietic elements and active bone remodeling were present in 36 valves (13%) with dystrophic calcification. Endochondral bone formation, similar to that seen in normal fracture repair, was identified in 4 valves. Microfractures were present in 92% of all valves with ossification. Neoangiogenesis was found in all valves with ossification. Bone morphogenetic proteins 2 and 4 (BMP 2/4), potent osteogenic morphogens, were expressed by myofibroblasts and preosteoblasts in areas adjacent to B- and T-lymphocyte infiltration in valves where ossification was identified. Mast cells were present in calcified and ossified valves and were especially prominent in atheromatous regions. ConclusionsHeterotopic ossification consisting of mature lamellar bone formation and active bone remodeling is a relatively common and unexpected finding in end-stage valvular heart disease and may be associated with repair of pathological microfractures in calcified cardiac valves.

Brain maturation is delayed in infants with complex congenital heart defects.

OBJECTIVE Small head circumferences and white matter injury in the form of periventricular leukomalacia have been observed in populations of infants with severe forms of congenital heart defects. This study tests the hypothesis that congenital heart defects delay in utero structural brain development. METHODS Full-term infants with hypoplastic left heart syndrome or transposition of the great arteries were prospectively evaluated with preoperative brain magnetic resonance imaging. Patients with independent risk factors for abnormal brain development (shock, end-organ injury, or intrauterine growth retardation) were excluded. Outcome measures included head circumferences and the total maturation score on magnetic resonance imaging. Total maturation score is a previously validated semiquantitative anatomic scoring system used to assess whole brain maturity. The total maturation score evaluates 4 parameters of maturity: (1) myelination, (2) cortical infolding, (3) involution of glial cell migration bands, and (4) presence of germinal matrix tissue. RESULTS The study cohort included 29 neonates with hypoplastic left heart syndrome and 13 neonates with transposition of the great arteries at a mean gestational age of 38.9 +/- 1.1 weeks. Mean head circumference was 1 standard deviation below normal. The mean total maturation score for the cohort was 10.15 +/- 0.94, significantly lower than reported normative data in infants without congenital heart defects, corresponding to a delay of 1 month in structural brain development. CONCLUSION Before surgery, term infants with hypoplastic left heart syndrome and transposition of the great arteries have brains that are smaller and structurally less mature than expected. This delay in brain development may foster susceptibility to periventricular leukomalacia in the preoperative, intraoperative, and postoperative periods.

Magnetic resonance scans should replace biopsies for the diagnosis of diffuse brain stem gliomas: a report from the Children's Cancer Group.

Childrens Cancer Group Protocol CCG-9882 was designed to determine the effectiveness of hyperfractionated radiation for the treatment of children and young adults with brain stem gliomas. The study opened for the accrual of patients on September 21, 1988, and was closed on June 30, 1991. The first 54 children in the study were treated with irradiation doses of 100 cGy given twice daily to a total dosage of 7200 cGy. The next 66 children were treated with a similar daily regimens to a total of 7800 cGy. Tumors were diagnosed by clinical and radiographic criteria. Decisions about the need for surgery were left to the discretion of the treating neurosurgeon; tissue diagnosis did not alter the therapy in patients with diffuse infiltrating tumors. We reviewed the neuroradiology and neurosurgery reports as well as the pathological specimens of children entered on the study. By magnetic resonance (MR) imaging criteria, tumors involved the majority of the brain stem in 76% of cases; only three patients had tumors localized to the midbrain or medulla. Operations were performed on 56 of 120 patients (47%). Cerebrospinal fluid shunts were inserted in 27 (23%) of the children; insertion of a shunt was the only operation in 11, and a shunt was inserted in conjunction with a tumor operation in 16. Tumor operations were performed in 45 (38%) of the patients; 24 had stereotactic biopsies, and 21 had craniotomies. Of the 21 patients who had craniotomies, only biopsies were performed in 11; partial tumor resections were performed in 5 patients and subtotal resection in 5.(ABSTRACT TRUNCATED AT 250 WORDS)

Computed tomography of shearing injuries of the cerebral white matter.

Changes secondary to shearing injury of the cerebral white matter can be demonstrated on CT. These consist of eccentric hemorrhage in the corpus callosum, diffuse cerebral swelling, subarachnoid hemorrhage and less frequently, hemorrhage around the third ventricular region and in the cerebral white matter. These CT findings are associated with acute severe neurologic deficits and sequelae. Eight cases with this injury pattern were encountered in 286 acute head injuries. All 8 patients were involved in automobile accidents.

Stroke Prevention Trial in Sickle Cell Anemia

Stroke occurs in 7-8% of children with Sickle Cell Disease (Hb SS) and is a major cause of morbidity. Rates of recurrence have been reduced from 46-90% to less than 10% through chronic blood transfusions. Prevention of first stroke, however, would be preferable because even one stroke can cause irreversible brain injury. Transcranial Doppler (TCD) ultrasound can detect arterial blood flow rates associated with subsequent stroke risk. By combining TCD screening and a potentially effective treatment, first stroke may be prevented. The Stroke Prevention Trial in Sickle Cell Anemia (STOP) is the first stroke prevention trial in Hb SS and the first randomized, controlled use of transfusion in Hb SS. This multi-center trial is designed to test whether reducing sickle hemoglobin to 30% or less with periodic blood transfusions will reduce first-time stroke by at least 70% compared to standard care. Primary endpoints will be clinically evident symptoms of cerebral infarction with consistent findings on Magnetic Resonance Imaging and Angiography (MRI/MRA) or symptomatic intracranial hemorrhage. Secondary endpoints will be asymptomatic brain lesions detected by MRI in brain areas not involved in primary endpoints. The design calls for a 6-month start-up interval, 18 months of TCD screening and randomization, and observation for stroke from entry through month 54. Key features of the trial are standardized TCD and MRI/MRA protocols interpreted blindly, and blinded adjudication of endpoints. The sample size (60 per treatment group) is based on prospective data relating TCD velocity to risk of stroke. A time-averaged mean velocity of > or = 200 cm/sec is associated with a 46% risk of cerebral infarction over 39 months. The sample size is sufficient to detect 70% reduction in the primary endpoint at 90% power. This trial will determine if transfusion is effective in the primary prevention of stroke. Secondary aims may further the understanding of the effects of transfusion on the brain and guide future research into cerebrovascular disease in Hb SS.

Pediatric Perfusion Imaging Using Pulsed Arterial Spin Labeling

To test the feasibility of pediatric perfusion imaging using a pulsed arterial spin labeling (ASL) technique at 1.5 T.

Pathophysiology, treatment and outcome following severe head injury in children.

The pathophysiology and outcome following severe head injury in 85 children are presented. The commonest initial CT diagnosis was of acute brain swelling. This swelling was associated with an increased white matter density on the CT scan which decreased to normal concomitant with recovery and increased ventricular size. CBF measurements in 6 of these patients revealed an increased blood flow despite a decreased CMRO2 and clinical coma. This CT pattern of diffuse swelling is believed to be due to acute cerebrovascular congestion and hyperemia and not to edema. Because of this, all children were treated with endotracheal intubation and controlled hyperventilation as part of the initial management. Mass lesions were uncommon, 20%. ICP was monitored in 40 children. The ICP rose above 20 Torr despite therapy in 80% of children with decerebrate or flaccid coma and in only 20% of children with spontaneous motor function. The ICP was at its highest between the second and fifth day. Aggressive therapy to control the ICP, with barbiturates if necessary, was successful in 80% of the patients. The overall results were useful recovery in 87.5% of the children, 3.5% were left vegetative or severely disabled and 9% died.

Pediatric brain stem gliomas.

Sixty‐two pediatric patients with brain stem glioma diagnosed between 1964 and 1978 have been reviewed. Posterior fossa exploration was performed on 53% of the patients. Pathology was obtained by biopsy in 58% of those explored. Fifty‐four patients had definitive radiation therapy with a median dose of 5000 rads. The actuarial five‐year survival for the entire group is 30%.

High Field Mr Imaging of Cerebral Venous Thrombosis

High field magnetic resonance (MR) imaging enables us to demonstrate the evolution of cerebral venous thrombosis. Initially, absence of a flow void and collateral venous channels are seen on T1 weighted images (WI). On T2WI thrombus appears hypointense. Hyperintensity is noted in an intermediate stage of thrombosis first on T1WI and later on T2WI. In the late stages recanalization of the vessel occurs with reappearance of the flow void. These findings are specific for venous thrombosis. High field MR may be the imaging modality of choice in the diagnosis of venous thrombosis.

Surveillance scanning of children with medulloblastoma.

BACKGROUND The standard follow-up care for children with medulloblastoma includes regular clinical evaluations and surveillance scanning of the central nervous system with computed tomography or magnetic resonance imaging. The evaluations and scanning assess the response of the tumor to treatment, detect any recurrence of disease, and monitor any complications of treatment. We compared the effectiveness of a periodic history taking and physical examination with that of surveillance scanning in detecting recurrent tumors. METHODS We reviewed the medical records, including 794 scanning reports or scans, of 86 children with posterior fossa medulloblastoma who were followed regularly between 1980 and 1991. Recurrent tumors were classified as symptomatic if neuroimaging studies had been prompted by clinical symptoms or signs and as radiographic if the tumor had been detected by imaging in an asymptomatic patient. RESULTS Twenty-three of the 86 children (27 percent) had a recurrence of tumor. Four recurrences (17 percent) were detected on scanning only, and 19 (83 percent) were associated with symptoms arising a median of four months after the previous scan. The median and range of survival after a recurrence of the tumor were 5 months and < 1 to 38 months, respectively, for a symptomatic recurrence and 20 months and 10 to 32 months, respectively, for a radiographic recurrence (P = 0.03). No patient survived after a recurrence. The longer survival of patients with recurrent tumors detected by scanning most likely reflects the small number of patients and lead-time and length biases associated with screening. CONCLUSIONS Among children with medulloblastoma, surveillance scanning is of little clinical value. Scanning detected a minority of recurrences, and no patient who had a recurrence survived.