Jens-Peter Schneider

Interventional and intraoperative MR: review and update of techniques and clinical experience

The concept of interventional magnetic resonance imaging (MRI) is based on the integration of diagnostic and therapeutic procedures, favored by the combination of the excellent morphological and functional imaging characteristics of MRI. The spectrum of MRI-assisted interventions ranges from biopsies and intraoperative guidance to thermal ablation modalities and vascular interventions. The most relevant recently published experimental and clinical results are discussed. In the future, interventional MRI is expected to play an important role in interventional radiology, minimal invasive therapy and guidance of surgical procedures. However, the associated high costs require a careful evaluation of its potentials in order to ensure cost-effective medical care.

Eye of the Tiger sign in multiple system atrophy

The Eye of the Tiger sign is the neuroradiological hallmark of patients with Pantothenate Kinase associated neurodegeneration and considered pathognomonic for patients carrying mutations in the PANK2 gene in this disease [1]. Here, we report a patient suffering from multiple system atrophy (MSA) and systemic lupus erythematodes with a typical Eye of the Tiger sign in T2-weighted MRI sequences. To our knowledge this is reported for the first time.

Investigation of time-dependency of intracranial brain shift and its relation to the extent of tumor removal using intra-operative MRI

Abstract The object of the paper is to investigate intra-operative brainshift and its relation to the extent of tumor removal. Repeated T1w 3D datasets were acquired at different time points intra-operatively (T0; T1; T2... Tx) using a vertical open 0.5T MR scanner in six patients with intracranial tumor. An offline analysis with initial linear registration, intensity adjustment and finally nonlinear registration of the first versus subsequent time points (T0/T1; T0/T2... T0/Tx) was performed, yielding a 3D displacement vector field that describes the brainshift. Brainshift was analysed qualitatively and quantitatively. A semi-automatic segmentation technique was used for calculation of the tumor size and the size of tumor remnants. Semi-automatic segmentation was reliable in all but two cases. Segmentation was difficult and unreliable in astrocytomas grade II. The shift basically followed gravity. The major shift reached levels up to 25 mm. Significant shift was observed at the first time point (T0). Intra-operative brainshift can be analysed qualitatively and also captured quantitatively. Neuronavigation that is based on pre-operatively acquired datasets is associated with a significant risk of surgical morbidity at a very early time point. Parallelisation on a workstation cluster may reduce computation time so that information about the displacement can facilitate updated navigation.

Evaluation of intra-operative ultrasound imaging in brain tumor resection: a prospective study

Abstract Aims: The purpose of our study was to evaluate intra-operative ultrasound (IOUS) as a tool of resection control after brain tumor surgery. In addition, we looked for tumor species suitable for ultrasound representation. Methods: Using a Siemens Omnia Sonoline Ultrasound, 36 tumors were examined, high-grade gliomas (62%), metastases (22%) and others (16%). We focused on tumor imaging by ultrasound with regard to its reliability of tumor expansion and margins. Evaluation of the images was carried out by correlating the ultrasound-based intra-operative measured tumor volume before and after resection with a pre- and post-operative (within 48 hours) measured volume by MRI. The IOUS measurements were performed by the neurosurgeon and the MRI measurements by the neuroradiologist. Thus, the measurement procedures were blinded. Corresponding to a deviation of the ultrasound volume by 10, 20 and > 20% from the MRI volume, the correlation was ranked good, moderate and poor. For assessing the agreement between these two methods of imaging, the statistical analysis was conducted using a method described by Bland and Altman. Results: High-grade gliomas mostly showed a moderate or poor correlation in comparing IOUS- and MRI-tumor volumetry resulting in incomplete resection. Metastases resulted in a good to moderate correlation with a satisfactory extent of resection. The other tumors had poor images with larger tumor residues. The MRI measured volumes tended to be larger on average; the deviation grew with tumor size. Conclusion: The reliability of IOUS depends on tumor type. It is beneficial to use IOUS for the resection of metastases and a few high-grade gliomas. Concerning the volumetric accuracy, the value of IOUS is worse than its value of navigation and resection control.

Effects of subthalamic nucleus stimulation on striatal dopaminergic transmission in patients with Parkinson’s disease within one-year follow-up

The mechanisms by which deep brain stimulation (DBS) of the subthalamic nucleus (STN) leads to clinical benefit in Parkinson’s disease (PD), especially with regard to dopaminergic transmission, remain unclear. Therefore, the objective of our study was to evaluate alterations of synaptic dopaminergic signaling following bilateral STN-DBS in advanced PD within a one-year follow-up. We used [123I]FP-CIT single-photon emission computed tomography (SPECT) to measure dopamine transporter (DAT) availability and [123I]IBZM SPECT to assess dopamine D2 receptor (D2R) availability (stimulator ON condition).Patients (n = 18) showed a tendency towards a better suppression of symptoms after STN-DBS (Unified Parkinson’s Disease Rating Scale motor score with medication decreased from 24. 1 ± 16. 1 to 15. 4 ± 7. 45; p = 0. 002) while medication was strongly reduced (61 % reduction of levodopa equivalent units; p < 0. 0001). No changes of striatal [123I]FP-CIT binding and an increase of [123I]IBZM binding up to 16 % (p < 0. 05) between pre-surgery and follow-up investigations were noticed. These data show that clinical improvement and reduction of dopaminergic drugs in patients with advanced PD undergoing bilateral STN-DBS are paralleled by stable DAT and recovery of striatal D2R availability 12 months after surgery.

Clinical Results in MR-Guided Therapy for Malignant Gliomas

The prognostic impact of the extent of tumour resection in surgery of malignant glioma patients remains controversial. We report the results of cumulative survival of malignant glioma patients operated with MR-guidance. Patients with complete tumour removal were compared with a population of patients with incomplete tumour removal. A 0.5 T scanner was used to criticize the extent of resection during surgery. In total no significant difference could be found, however there is a tendency that complete tumour removal seems to be associated with a slightly increased median survival time.

Vascular parkinsonism in a CADASIL case with an intact nigrostriatal dopaminergic system

5 % of cerebral small vessel diseases manifesting mostly between the age of 40 and 60 years irrespective of vascular risk factors [1]. The clinical spectrum includes migraine, recurrent subcortical strokes, cognitive decline, and psychiatric manifestations [1, 2]. Here, we report for the first time a case of vascular parkinsonism and dementia showing functional integrity of the nigrostriatal dopaminergic system diagnosed as CADASIL by skin biopsy. A 55-year old male presented to our department with a two year history of reduced mobility, cognitive decline, chronic fatigue, and urinary incontinence. Previous diagnosis included major depression, however, the antidepressant therapy with mirtazapin was ineffective. Amisulpride had been administered due to hypochondric delusions. Hypertension and atrial fibrillation were treated adequately with metoprolol, digitoxin, and phenprocoumon, otherwise his LETTER TO THE EDITORS

Reconstructive and ophthalmologic outcomes following resection of spheno-orbital meningiomas.

Purpose: To assess long-term stability and aesthetic and functional outcomes of orbital reconstruction after resection of spheno-orbital meningiomas using calvarial bone grafts. Methods: A series of 21 patients were retrospectively examined after an average follow-up period of 65.6 months with regard to their personal satisfaction and also proptosis, ocular function, and reconstructive outcome. The sagittal position of the globe was analyzed by CT and MRI. Patients were treated surgically in an interdisciplinary approach between 1997 and 2006. Results: A permanent postoperative decrease in globe protrusion of 2.7 mm on average was achieved. Most patients (76%) reported identical or improved vision, 85% were satisfied with the reconstructive result, and 55% were free of discomfort in daily life. Seven patients suffered from recurrences that were invariably accompanied by globe protrusion. Conclusions: Calvarial bone grafts provide good, stable long-term results in the reconstruction of orbital defects. Globe protrusion is a reliable indicator for the detection of recurrences in spheno-orbital meningiomas. Because of high recurrence rates, it is advisable to continue follow-up for 20 or more years.

Responsiveness to a dopamine agent in Holmes tremor – case report

Sirs, Holmes tremor has been linked to midbrain lesions affecting the red nucleus and neighboring structures. Treatment of Holmes tremor remains difficult. We report the successful treatment of a case with Holmes tremor with a dopamine agent for the first time. A homosexual man (51 years) was admitted to our department in July 2004 for weakness of his right arm and horizontal double vision that had gradually developed over 5 days. Clinical examination revealed Weber’s syndrome: left-sided external oculomotor palsy, right-sided facial hypesthesia and right-sided hemiparesis. MR imaging showed a 1.5 cm · 1.4 cm · 1.8 cm lesion within the midbrain affecting the left red nucleus and neighboring structures including the left cerebral peduncle that was isointense with surrounding edema on T1and T2weighted sequences with ring-like enhancement after administration of contrast agent. Abscess formation was suspected. Lumbar puncture showed 6 leukocytes/ ll, elevated total protein (524 mg/l) with intrathecal immunoglobulin G (IgG) synthesis, indicating central nervous system (CNS) inflammation. Bone marrow biopsy showed decreased CD4/CD8 ratio but normal hematopoietic differentiation with reactive leukocytosis. Human immunodeficiency virus enzyme immunoassay (HIV EIA) and Western blot were positive and acquired immunodeficiency syndrome (AIDS) was diagnosed, with cerebral toxoplasmosis as AIDSdefining illness. The patient was started on pyrimethamine 500 mg b.i.d., clindamycin 600 mg q.i.d. and Lamivudin 150 mg plus Zidovudin 300 mg b.i.d., Efavirenz 600 mg daily, Lopinavir 1200 mg plus 300 mg Ritonavir b.i.d. During the following weeks, his double vision remitted and right-sided hemiparesis improved, while the lesion slowly regressed. In May 2005, the patient returned to our outpatient clinic complaining of tremor in his right arm that had slowly evolved over the previous 5 months. Examination revealed latent right-sided hemiparesis and additional severe resting tremor that was also present with action. No rigidity or other movement disorders were present, nor diplopia. Holmes tremor was suspected. As the lesion had also affected substantia nigra previously, we performed [I] FP-CIT: Ioflupane (DatSCAN, General Electric Healthcare, Munich, Germany) SPECT to assess dopamine transporter function (see Fig. 1). This analysis showed left-sided reduction of dopamine transporter (DAT) availability. We started dopaminomimetic therapy using the dopamine agonist pramipexole, gradually increasing the dosage to 2.8 mg daily. Resting tremor was dramatically reduced and kinetic tremor improved gradually. The effect persisted until May 2006, when the patient was hospitalized for nephrolithiasis and pramipexole was discontinued. The severe resting tremor reappeared and again remitted after reintroduction of pramipexole after surgery. Holmes tremor is an irregular tremor at rest and during movements that typically starts with a variable delay (2 months to 2 years) after an acute midbrain lesion. Lesions of red nucleus alone are not sufficient to cause oscillatory activity. Concomitant deficits of cerebellothalamic and nigrostriatal fibers are necessary. Treatment is often unsatisfactory and increasingly deep-brain stimulation has been introduced to treat Holmes tremor [1]. Corresponding to the mixed pathology, two leads might be more appropriate than one [2]. Levodopa was used successfully in some cases [3], but the effect of dopamine agents has not been reported. In our patient, resting tremor was almost totally abolished, whereas kinetic tremor persisted to some degree. Our finding concerning DAT availability is in concordance with earlier positron emission tomography (PET) data [4]. Recent studies suggested that pramipexole is no more effective than other dopamine agents in controlling tremor in Parkinson’s disease [5]. Therefore, we do not expect

Subcortical Right Parietal AVM Rotational vertigo and caloric stimulation fMRI support a parietal representation of vestibular input.

Sirs: Cortical vestibular projection areas in humans have been identified by functional magnetic resonance imaging (fMRI) [5, 10, 13], SPECT [14] and PET [2]. Intracerebral electrical stimulation in epilepsy patients has confirmed many of these results [7]. The parietoinsular cortex appears to be the dominant region, with right-sided accentuation [3], with additional temporal and frontal regions [2, 5, 10, 13]. The most essential afferent vestibular pathway is thought to run via the nucleus ventralis posterior inferior thalami to a cortical parietal region around the intraparietal sulcus [12]. Clinically, supratentorial lesions as the cause of vestibular disorders with rotational vertigo have rarely been documented [1, 4, 8]. A 26-year-old man presented with rotational vertigo and a feeling of body traction and tilt to the right side (“as if making a right turn on a bicycle”), with no associated nausea or auditory disturbance. Symptoms lasted for several hours, waxing and waning. Similar symptoms had occurred and spontaneously remitted once before. He had suffered an intraventricular supratentorial hemorrhage six years earlier, when investigations including digital subtraction angiography (DSA) were normal. The neurological examination was entirely normal, including a comprehensive set of neuro-ophthalmological and neuro-otological bed-side tests. Caloric stimulation revealed regular excitability of the vestibular apparatus bilaterally without pathological nystagmus. There was no hypacusis. Routine EEG, performed on two separate occasions, was normal. Cranial MRI detected a hyperintense lesion of approximately 7 mm in the parietal white matter adjacent to the posterior horn of the right lateral ventricle (Fig. 1a) with punctate contrast enhancement and signal voids (Fig. 1b). There was no evidence for prior parenchymal hemorrhage on T2*weighted gradient echo images, and no abnormalities in the brainstem or cerebellum. An arteriovenous malformation (AVM) was suspected and confirmed by DSA (Fig. 1c). Functional MRI was performed with caloric stimulation (separate cold-water (4°C) irrigation of right and left external meatus [13]). Leftsided stimulation led to activation in the inferior parietal lobulus and the supramarginal gyrus bilaterally, predominantly on the right side (Fig. 2). This result is consisLETTER TO THE EDITORS