Can We Rely on Susceptibility-Weighted Imaging for Subthalamic Nucleus Identification in Deep Brain Stimulation Surgery?

BACKGROUND

Susceptibility-weighted imaging (SWI) offers significantly improved visibility of the subthalamic nucleus (STN) compared with traditional T2-weighted imaging. However, it is unknown whether the representation of the nucleus on SWI corresponds to the neurophysiological location of the STN.

OBJECTIVE

To determine the correlation between the intraoperative electrophysiological activity of the STN and the representation of the nucleus on different magnetic resonance imaging (MRI) sequences used for deep brain stimulation target planning.

METHODS

At stereotactic target depth, microelectrode recordings (MERs) of typical STN neuronal activity were mapped on 3 different preoperative MRI sequences: 1.5-T SWI, 1.5-T T2-weighted, and 3-T T2-weighted MRI. For each MRI sequence, it was determined whether the MER signal was situated inside or outside the contour of the STN.

RESULTS

A total of 196 MER tracks in 34 patients were evaluated. In 165 tracks (84%), typical electrophysiological STN activity was measured. MER activity was situated more consistently inside hypointense STN contour representation on 1.5- and 3-T T2-weighted images compared with SWI (99% and 100% vs 79%, respectively). The 21% incongruence of electrophysiological STN activity outside the STN contour on SWI was seen almost exclusively in the anterior and lateral microelectrode channels.

CONCLUSION

STN representation on SWI does not correspond to electrophysiological STN borders. SWI does not correctly display the lateral part of the STN. When aiming to target the superolateral sensorimotor part of the STN during deep brain stimulation surgery, SWI does not offer an advantage but a disadvantage compared with conventional T2. Future research is needed to determine whether these findings may also apply for high-field SWI.

Imaging in lower urinary tract infections

In epididymo-orchitis, a sonogram shows a non-homogenous and hypertrophied epididymis and testis, with increased vascularisation seen on a Doppler sonogram. Abscesses must be investigated using sonography so that a necrotic tumour is not misdiagnosed. In prostatitis, sonography is indicated to investigate urine retention and where treatment has failed (to look for a blockage, an abscess, or pyelonephritis). Endorectal sonography is the best imaging modality for analysing the parenchyma, but otherwise has limited value. Chronic prostatitis is the main differential diagnosis from prostate cancer; the two may be distinguished using diffusion MRI. In cases of cystitis, imaging is indicated when a patient has recurrent cystitis (to investigate what the causative factors might be), or an infection with a less common bacterium (to look for calcifications, emphysema, any involvement of the upper urinary tract), and in cases of cystitis with pseudotumour.

Top-down-directed synchrony from medial frontal cortex to nucleus accumbens during reward anticipation

The nucleus accumbens and medial frontal cortex (MFC) are part of a loop involved in modulating behavior according to anticipated rewards. However, the precise temporal landscape of their electrophysiological interactions in humans remains unknown because it is not possible to record neural activity from the nucleus accumbens using noninvasive techniques. We recorded electrophysiological activity simultaneously from the nucleus accumbens and cortex (via surface EEG) in humans who had electrodes implanted as part of deep-brain-stimulation treatment for obsessive-compulsive disorder. Patients performed a simple reward motivation task previously shown to activate the ventral striatum. Spectral Granger causality analyses were applied to dissociate "top-down" (cortex → nucleus accumbens)- from "bottom-up" (nucleus accumbens → cortex)-directed synchronization (functional connectivity). "Top-down"-directed synchrony from cortex to nucleus accumbens was maximal over medial frontal sites and was significantly stronger when rewards were anticipated. These findings provide direct electrophysiological evidence for a role of the MFC in modulating nucleus accumbens reward-related processing and may be relevant to understanding the mechanisms of deep-brain stimulation and its beneficial effects on psychiatric conditions.

Potential efficacy of enzyme replacement and substrate reduction therapy in three siblings with Gaucher disease type III

We report three siblings with Gaucher disease type III, born between 1992 and 2004. During this period, new developments resulted in different potential therapies, changing clinical practice. The two eldest siblings received enzyme replacement therapy (ERT) from the age of 24 and 5 months respectively, later followed by an increase in dosage. ERT was combined with substrate reduction therapy (SRT) from the ages of 12 and 8 years, respectively. In the youngest sibling the combination of high-dose ERT and SRT was given from the age of 5 months. The two eldest siblings showed significant neurological impairment from the age of 1.5 years, starting with a convergent strabismus and partial oculomotor apraxia, followed by cognitive decline and an abnormal EEG and BAER. In contrast, the neurological development in the youngest sibling is almost completely normal. At the age of 3 years, cognitive development, EEG and BAER are all normal. Disturbed saccadic eye movements, which were already present at the start of therapy, remained stable. In addition to the clinical efficacy, we report on the biochemical response to therapy. Based on our results, the combination of high-dose ERT and SRT should be considered as a possible therapeutic approach for GD III, especially if started at a young age. Further follow-up studies are necessary to explore the long-term therapeutic effects.

Antisaccade deficit is present in young first-episode patients with schizophrenia but not in their healthy young siblings

BACKGROUND

Results of studies on antisaccade (AS) deficit in relatives of patients with schizophrenia are inconclusive. We hypothesized that AS performance in siblings of patients with schizophrenia is worse than in healthy controls and better than in patients with schizophrenia.

METHOD

We included 55 first-episode patients with schizophrenia, 28 healthy siblings and 36 healthy controls to evaluate AS performance. Eye movements were measured electromagnetically by the double magnetic induction (DMI) method.

RESULTS

Patients with schizophrenia had a significantly higher error rate than siblings (d=0.86, p<0.0001) and controls (d=1.35, p<0.0001). Siblings had a higher mean error rate than healthy controls but this did not reach significance (d=0.56, p=0.29). The intra-class correlation (ICC) was 0.33 for the error rate. Mean AS gain was higher in siblings than in patients (d=0.75, p=0.004) and controls (d=0.6, p=0.05). The ICC was 0.08.

CONCLUSION

As parameters in strictly screened healthy young siblings of young first-episode patients with schizophrenia are comparable to results found in studies investigating older relatives. However, the statistical results (i.e. the ICCs) suggest that there is little evidence of shared environmental or genetic factors on error rate variation.

Antisaccade task performance in patients at ultra high risk for developing psychosis

Patients with schizophrenia consistently perform worse than healthy controls on the antisaccade task in which the subject is required to inhibit a reflexive saccade to a suddenly appearing visual target and look in the opposite direction. To our knowledge there is no research yet showing how patients at ultra high risk (UHR) for developing psychosis perform on the antisaccade task. The aim of the present study was to investigate antisaccade task performance in UHR patients. Patients were eligible for the study when they met criteria for one or more of the following groups: Attenuated symptoms or brief limited intermitted psychotic symptoms or a first-degree family member with a psychotic disorder and reduced functioning or basic symptoms. In 35 UHR patients we assessed antisaccades, neuropsychological test performance and symptomatology. Antisaccade task results were compared with those obtained in 42 age- and intelligence-matched patients with recent-onset schizophrenia and 28 matched healthy controls. Antisaccade error rate was significantly higher in the UHR patients than in the controls. Schizophrenia patients performed worse than the UHR patients and the control subjects. We found a trend towards higher antisaccade error rate at baseline in the UHR patients who later made the transition to psychosis compared to the UHR patients who did not make the transition to psychosis. Poor spatial working memory function was related to increased antisaccade errors in the UHR group. Abnormal antisaccade task performance is also present in patients at UHR for developing psychosis. Subsequent research needs to clarify if increased antisaccade error rate is predictive of a psychotic episode. In UHR patients, poor antisaccade performance may reflect working memory dysfunction.

A unique achiasmatic anomaly detected in non-albinos with misrouted retinal-fugal projections

In mammals with binocular vision, projections of retinal axons to primary retino-recipient nuclei establish a strict visuotopic and eye-segregated arrangement. Normal primate visual pathway organization is characterized by orderly hemiretina separation in which nasal-retinal axons cross at the optic chiasm and project to primary contralateral subcortical and cortical structures while temporal-retinal fibres project ipsilaterally to corresponding visual structures. We report here, in two unrelated children, an unusual visual pathway malformation in which nasal-retinal cortical projections, unable to decussate due to the inborn absence of an optic chiasm, erroneously route ipsilaterally to visual projection targets. We have termed this newly documented achiasmatic condition the non-decussating retinal-fugal fibre syndrome (Apkarian et al., Invest. Ophthalmol. Vis. Sci., 34, Suppl., 711, 1993).