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Peter W. Carmel and Fritz J. Cramer

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Early descriptions of the Arnold-Chiari malformation

The contribution of John Cleland

Peter W. Carmel and William R. Markesbery

✓ John Cleland described an unusual congenital anomaly of the brain stem in 1883 in which the medulla was elongated, the fourth ventricle extended into the cervical canal, and the inferior vermis distorted caudally. In 1891 Chiari described two types of brain stem malformation; in one the cerebellar tonsils extended into the cervical canal without medullary deformation, while in the other there was caudal extension of the brain stem and cerebellum and prolongation of the inferior vermis into the cervical canal. The second type was termed the “Arnold-Chiari” malformation by other authors in 1907, and corresponds to the condition described earlier by Cleland. The anatomical features and differences between the types of malformation are tabulated.

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Peter W. Carmel, Richard A. R. Fraser and Bennett M. Stein

✓ The results of suboccipital craniectomy for varying types of posterior fossa pathology in 50 children are reported. Thirty-five (70%) experienced aseptic meningitis postoperatively, with spiking fever and meningismus; cerebrospinal fluid (CSF) studies revealed pleocytosis, high protein values, and depression of glucose. The absence of bacterial pathogens in serial CSF cultures distinguishes this syndrome from septic meningitis. Aseptic meningitis does not respond to antibiotics, but steroids in suitable doses will modify or suppress the clinical and CSF picture. This syndrome may predispose to postoperative hydrocephalus, but steroid therapy may diminish this risk.

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J. Lobo Antunes, Peter W. Carmel, Edgar M. Housepian and Michel Ferin

✓ Luteinizing hormone (LH) and LH-releasing hormone (LHRH) were measured by radioimmunoassay in blood samples collected from the pituitary gland during transsphenoidal surgery in 19 patients. Detectable levels of LHRH were present in 12 patients. Wide fluctuations of LHRH were seen in sequential samples collected at 10-minute intervals, suggesting a pulsatile mode of release. This technique may yield useful data on hypothalamic control of pituitary secretion.

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Peter W. Carmel, J. Lobo Antunes and Michel Ferin

✓ A transorbital, transsphenoidal microsurgical approach to the pituitary stalk and gland was used to collect blood from the hypothalamo-hypophyseal portal system in monkeys. Specimens may be obtained from the entire pituitary stalk, individual long portal veins, or the pituitary sinusoidal bed, with little risk of mortality. Continuous stalk blood sampling was carried out for periods of up to 10 hours. Pituitary sinusoidal-system blood was also collected during transsphenoidal surgery in man. The uses of data concerning hypothalamic-hypophyseal regulation obtained by these methods are illustrated.

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Saul Balagura, Andrew G. Frantz, Edgar M. Housepian and Peter W. Carmel

✓ Serum prolactin levels were determined in 205 patients with a variety of intracranial diseases, including 70 cases with pituitary tumors. It is concluded that although the absence of elevated prolactin levels does not help to rule out pituitary pathology, the presence of hyperprolactinemia is highly specific for diseases of the pituitary and hypothalamus, and prolactin determination should be part of the regular work-up of pituitary tumor suspects. Excluding known causes of hyperprolactinemia, such as tranquilizing drug ingestion, the presence of neurological disease outside the hypothalamic-pituitary area was not associated with increased serum prolactin concentrations.

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Abraham Kader, James T. Goodrich, William J. Sonstein, Bennett M. Stein, Peter W. Carmel and W. Jost Michelsen

✓ Angiography has been considered to be the gold standard to judge the success of treatment for cerebral arteriovenous malformations (AVMs). Patients without residual nidus or early draining veins on postoperative angiograms are considered cured, with the risk of hemorrhage eliminated. A series of five patients with recurrent AVMs after negative postoperative angiography is described. All patients had hemispheric AVMs, presented initially with hemorrhage, and were between 5 and 13 years of age. Recurrence was noted 1 to 9 years later (at 12–16 years of age); after a hemorrhage in three patients, seizures in one, and on follow-up magnetic resonance imaging in one. Four patients underwent angiography that showed recurrence of the AVM at or adjacent to the original site. Three years postsurgery, the fifth patient died from a large intracerebral and intraventricular hemorrhage originating in the previous location of the AVM; however, the patient did not undergo angiography at the time of recurrence. The initial negative angiograms obtained postoperatively in these patients may be explained by postoperative spasm or thrombosis of a small residual malformation. However, in the authors' cumulative experience with 808 patients who have undergone complete surgical removal of AVMs (of whom 667 were older than 18 years of age), no case of recurrent AVM has been observed in an adult. Therefore, actual regrowth of an AVM may occur in children and could be a consequence of their relatively immature cerebral vasculature and may involve active angiogenesis mediated by humoral factors. The present findings argue against the assumption that AVMs are strictly congenital lesions resulting from failure of capillary formation during early embryogenesis. It is concluded that delayed imaging studies should be considered in children at least 1 year after their initial negative postoperative arteriogram to exclude a recurrent AVM.

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Michael Schulder, Joseph A. Maldjian, Wen-Ching Liu, Andrei I. Holodny, Andrew T. Kalnin, In Ki Mun and Peter W. Carmel

Object. The purpose of this study was to evaluate the efficacy of noninvasive preoperative functional imaging data used in an interactive fashion in the operating room. The authors describe a method of registering preoperative functional magnetic resonance (fMR) imaging localization of sensorimotor cortex with a frameless stereotactic surgical navigation device.

Methods. The day before surgery, patients underwent blood oxygen level—dependent fMR imaging while performing a finger-tapping motor paradigm. Immediately afterward an anatomical stereotactic MR image was acquired. Raw fMR imaging data were analyzed offline at a separate workstation, and the resulting functional maps were registered to a high-resolution anatomical scan. The fused functional—anatomical images were then downloaded onto a surgical navigation computer via an ethernet connection. At surgery, the brain was exposed in the standard fashion, and the sensorimotor cortex was identified by direct cortical stimulation, the use of somatosensory evoked potentials, or both. This localization was then compared with that predicted by the registered fMR study.

Thirteen procedures were performed in 12 patients. The mean registration error was 2.2 mm. The predicted location of motor and/or sensory cortex matched that found on intraoperative mapping in all 12 patients tested. Maximal tumor resection was accomplished in each case and no new permanent neurological deficits resulted.

Conclusions. Compared with conventional brain mapping techniques, fMR image—guided surgery may allow for smaller brain exposures, localization of the language cortex with the patient under general anesthesia, and the mapping of multiple functional sites. The scanning equipment used in this method may be more readily available than for other functional imaging techniques such as positron emission tomography or magnetoencephalography.

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Peter W. Carmel, A. Leland Albright, P. David Adelson, Alexa Canady, Peter Black, William Boydston, David Kneirim, Bruce Kaufman, Marion Walker, Mark Luciano, Ian F. Pollack, Kim Manwaring, M. Peter Heilbrun, I. Richmond Abbott and Harold Rekate

Shunt systems with differential pressure valves are prone to the complications of overdrainage. A programmable valve permits adjustment of the opening pressure of the valve. In this paper the authors report the incidence of subdural fluid collections in a randomized trial of programmable compared with conventional valves, and they describe methodologies used in management of this complication.

A multiinstitutional, prospective, randomized trial of the Codman Hakim programmable valve and conventional fixed-pressure valves was undertaken. Two classes were defined: “new” and “replacement” valves. Randomization of the type of valve in each group was performed at each study site. Clinical and radiological studies were required at fixed intervals over a 104-week period. All complications were reported. The experimental valves were required to be reprogrammed after magnetic resonance imaging studies, but all other decisions regarding pressure setting were left to each investigator.

Three hundred seventy-seven patients were randomized; 194 were treated with a programmable valve and 183 with a fixed-pressure valve. The two groups were statistically similar in demographic composition, as were the “new” and “replacement” categories. The investigators made 540 valve pressure changes (five per patient; range one-41 changes). More than half of the reprogramming adjustments were made in the first 3 months postplacement; 70% were made within 6 months. More than half of all reprogramming adjustments were required in a group of 30 patients.

Four treatment modalities were observed: 1) 30% of the fluid collections resolved spontaneously (25% in the patients with programmable valves and 36.3% in those with conventional valves) and were largely found to be hygromas in infants and children; 2) four subdural fluid collections were unresolved and under observation; 3) the subdural hematoma was drained and the shunt removed (in 8.3% of patients with the programmable valve and 36.3% of those with the control valve); 4) the pressure of programmable valve was raised in 58% of patients (seven of 12), and this increase in opening pressure was a feature used by investigators to affect treatment.

There was no significant difference in the incidence of subdural fluid collections between the programmable and fixed-pressure valve treatment groups. The programmable feature provided a considerable advantage in treatment when subdural collections occurred.