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Erich O. Richter and David W. Pincus

✓Dandy–Walker malformation (DWM) is a well-described clinical entity, which includes vermian agenesis, posterior fossa cysts, and frequently, hydrocephalus. The authors report the clinical course and present the radiographic findings pertaining to a 1-month-old girl with DWM who was treated initially with a ventriculoperitoneal shunt and endoscopic fenestration of a posterior fossa cyst. After decompression for hydrocephalus, an increased mass effect at the foramen magnum from her posterior fossa cyst was demonstrated, as well as subsequent development of syringohydromyelia from C-4 to T-7. She was treated with a cystoperitoneal shunt. At the 6-month follow-up examination, the child (15 months of age) had achieved gains in developmental milestones, and complete resolution of the syrinx was established through MR imaging. This is the fourth nonautopsy pediatric case of DWM-associated syringohydromyelia reported in the literature, and the third in a child to demonstrate impaction of the posterior fossa cyst at the foramen magnum leading to syrinx formation with subsequent treatment and resolution. Spinal imaging may be useful in the evaluation of patients with DWM who do not experience expected improvement after shunt procedures.

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Erich O. Richter, Tasnuva Hoque, William Halliday, Andres M. Lozano and Jean A. Saint-Cyr

Object. The subthalamic nucleus (STN) is a target in surgery for Parkinson disease, but its location according to brain atlases compared with its position on an individual patient's magnetic resonance (MR) images is incompletely understood. In this study both the size and location of the STN based on MR images were compared with those on the Talairach and Tournoux, and Schaltenbrand and Wahren atlases.

Methods. The position of the STN relative to the midcommissural point was evaluated on 18 T2-weighted MR images (2-mm slices). Of 35 evaluable STNs, the most anterior, posterior, medial, and lateral borders were determined from axial images, dorsal and ventral borders from coronal images. These methods were validated using histological measurements in one case in which a postmortem examination was performed.

The mean length of the anterior commissure—posterior commissure was 25.8 mm. Subthalamic nucleus borders derived from MR imaging were highly variable: anterior, 4.1 to −3.7 mm relative to the midcommissural point; posterior, 4.2 to 10 mm behind the midcommissural point; medial, 7.9 to 12.1 mm from the midline; lateral, 12.3 to 15.4 mm from the midline; dorsal, 0.2 to 4.2 mm below the intercommissural plane; and ventral, 5.7 to 9.9 mm below the intercommissural plane.

The position of the anterior border on MR images was more posterior, and the medial border more lateral, than its position in the brain atlases. The STN was smaller on MR images compared with its size in atlases in the anteroposterior (mean 5.9 mm), mediolateral (3.7 mm), and dorsoventral (5 mm) dimensions.

Conclusions. The size and position of the STN are highly variable, appearing to be smaller and situated more posterior and lateral on MR images than in atlases. Care must be taken in relying on coordinates relative to the commissures for targeting of the STN.

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Hans-Peter Richter, Erich Kast, Rainer Tomczak, Werner Besenfelder and Wilhelm Gaus

Object. Failed-back syndrome is still an unsolved problem. Use of ADCON-L gel, already commercially available, has been proven to reduce postoperative scarring in animal experiments. The authors of two controlled clinical studies have also shown positive results when applying the gel. They did not, however, establish patient-oriented endpoints. The authors report a study of ADCON-L in which they focus on patient-oriented endpoints.

Methods. Patients with lumbar disc herniation were randomized to an ADCON-L—treated or control group. Therapeutic success was evaluated using the validated Hannover Questionnaire on Activities of Daily Living (FFbH) 6 months after surgery. The study took place between November 14, 1996, and April 20, 1998, in eight neurosurgical centers in Germany. A total of 398 patients was recruited; 41 patients dropped out during follow up.

The mean functional FFbH score (100 points = all activities are possible without problem; 0 points = no activity is possible) was 78.5 points in the ADCON-L—treated group compared with 80 points in the control group. Furthermore, in terms of secondary outcome variables, the ADCON-L group did not have an advantage over the control group. Only the mean magnetic resonance imaging score showed a slight advantage of ADCON-L over the control group.

Conclusions. The authors found no positive effect of treatment with ADCON-L gel in patients in whom one-level lumbar microdiscectomy was performed. Because of its rather large sample size and its homogeneity, the study had sufficient power to detect even small differences between the two groups.

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Robert A. Mericle, Erich O. Richter, Eric Eskioglu, Courtney Watkins, Laszlo Prokai, Christopher Batich and Swadeshmukul Santra

Object

The authors describe a novel concept for brain mapping in which an endovascular approach is used, and they demonstrate its feasibility in animal models. The purpose of endovascular brain mapping is to delineate clearly the nonfunctional brain parenchyma when a craniotomy is performed for resection. The nonfunctional brain will be stained with sharp visual margins, differentiating it from the functional, nonstained brain. The authors list four essential criteria for developing an ideal endovascular mapping agent, and they describe seven potential approaches for accomplishing a successful endovascular brain map.

Methods

Four Sprague–Dawley rats and one New Zealand white rabbit were used to determine initial feasibility of the procedure. The animals were anesthetized, and the internal carotid artery was catheterized. Four potential brain mapping agents were infused into the right hemisphere of the five animals. Afterward, the brains were removed and each was analyzed both grossly and histologically.

Fluorescein and FD&C Green No. 3 provided good visual clarity and margins, but required blood–brain barrier (BBB) manipulation. Tantalum particles enabled avoidance of BBB manipulation, but provided inadequate visual clarity, probably because of their size. A Sudan black “cocktail” provided excellent clarity and margins despite remaining in the brain capillaries.

Conclusions

This is a novel application of the endovascular approach, and has broad potential for clinical neurosurgical brain mapping. The animal models in this study establish the feasibility of the procedure. However, further study is required to demonstrate safety, minimize toxicity, investigate stain durability, and improve the characteristics of potential mapping agents. The authors are planning to conduct future studies for identification of mapping agents that do not require BBB manipulation or vascular occlusion.

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David W. Pincus, Erich O. Richter, Anthony T. Yachnis, Jeffrey Bennett, M. Tariq Bhatti and Amy Smith

Object

Although it is widely accepted that biopsy sampling is not indicated for the diagnosis and empiric treatment of diffuse pontine glioma, it is common to encounter patients with brainstem lesions that cannot be diagnosed on the basis of imaging studies alone. In cases not amenable to resection, a tissue diagnosis may still be necessary to make appropriate treatment recommendations. The authors retrospectively reviewed their institutional experience with stereotactic biopsy procedures in pediatric patients during a 4-year period.

Methods

A three-dimensional graphics workstation was used for trajectory planning to obtain biopsy samples of brainstem lesions in 10 patients. One patient experienced mild diplopia postoperatively. No other morbidity was noted; no patient died as a result of the procedure. The biopsy procedure yielded a pathological diagnosis in all cases. A later resection in one patient resulted in a change in diagnosis. Overall, the pathological findings were varied, and in some cases the tissue diagnosis altered the treatment recommendations.

Conclusions

The findings in this small series suggest that brainstem stereotactic biopsy sampling in children is a safe procedure with a high diagnostic yield. In patients in whom radiographic findings are not consistent with diffuse pontine glioma and resection is not appropriate, stereotactic biopsy sampling should be considered.

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Andreas Stadlbauer, Michael Buchfelder, Christopher Nimsky, Wolfgang Saeger, Erich Salomonowitz, Katja Pinker, Gregor Richter, Hiroyoshi Akutsu and Oliver Ganslandt

Object

The aim of this study was to correlate proton MR (1H-MR) spectroscopy data with histopathological and surgical findings of proliferation and hemorrhage in pituitary macroadenomas.

Methods

Quantitative 1H-MR spectroscopy was performed on a 1.5-T unit in 37 patients with pituitary macroadenomas. A point-resolved spectroscopy sequence (TR 2000 msec, TE 135 msec) with 128 averages and chemical shift selective pulses for water suppression was used. Voxel dimensions were adapted to ensure that the volume of interest was fully located within the lesion and to obtain optimal homogeneity of the magnetic field. In addition, water-unsuppressed spectra (16 averages) were acquired from the same volume of interest for eddy current correction, absolute quantification of metabolite signals, and determination of full width at half maximum of the unsuppressed water peak (FWHMwater). Metabolite concentrations of choline-containing compounds (Cho) were computed using the LCModel program and correlated with MIB-1 as a proliferative cell index from a tissue specimen.

Results

In 16 patients harboring macroadenomas without hemorrhage, there was a strong positive linear correlation between metabolite concentrations of Cho and the MIB-1 proliferative cell index (R = 0.819, p < 0.001). The metabolite concentrations of Cho ranged from 1.8 to 5.2 mM, and the FWHMwater was 4.4–11.7 Hz. Eleven patients had a hemorrhagic adenoma and showed no assignable metabolite concentration of Cho, and the FWHMwater was 13.4–24.4 Hz. In 10 patients the size of the lesion was too small (< 20 mm in 2 directions) for the acquisition of MR spectroscopy data.

Conclusions

Quantitative 1H-MR spectroscopy provided important information on the proliferative potential and hemorrhaging of pituitary macroadenomas. These data may be useful for noninvasive structural monitoring of pituitary macroadenomas. Differences in the FWHMwater could be explained by iron ions of hemosiderin, which lead to worsened homogeneity of the magnetic field.