Holger Wenz

Primary motor cortex activation and lateralization in patients with tumors of the central region.

Hemispheric lateralization is a frequently encountered phenomenon of cortical function. It describes the functional specialization of a region on one side of the brain for a given task. It is well characterized in motor and sensory, as well as language systems and becomes more and more known for various cognitive domains. While in the adult healthy brain hemispheric lateralization is mostly set, pathological processes may lead to cortical reorganization. In these cases neuroplasticity of the corresponding region in the non-dominant hemisphere seems to play an important role. In a previous study we investigated language associated regions in right-handed patients with frontal and temporal tumors of the left hemisphere. We observed a marked change of language lateralization in these patients towards the non-dominant hemisphere as measured by functional MRI (Partovi et al., 2012). In the present study we evaluated activation and lateralization of cortical motor areas in patients with tumors of the central region. BOLD fMRI was performed during unilateral voluntary movements of the contralesional hand in 87 patients. Individual correlations of measured BOLD-signals with the model hemodynamic reference function were determined on a ROI basis in single subjects and compared to those of 16 healthy volunteers. In volunteers the strongest activation is usually found in the M1 hand representation contralateral to the movement, while a weaker homotopic co-activation is observed in ipsilateral M1 (Stippich et al., 2007a). In the patient group our results show significant changes of motor activations, ranging from a reduction of M1 lateralization to equalization of M1 activations or even inversion of M1 lateralization during contralesional movements. This study corroborates in a large patient group the idea that lesions affecting M1 may lead to functional reorganization of cortical motor systems and in particular equalize hemispheric lateralization. However, it is not yet clear whether these changes are only an epiphenomenon or indeed reflect an attempt of recovery of brain function.

Acute Marchiafava-Bignami disease with extensive diffusion restriction and early recovery: case report and review of the literature.

Marchiafava‐Bignami disease (MBD) is a neurological disorder that has been found to be associated with chronic alcoholism and malnutrition. MBD classically results in acute edema and demyelination of the corpus callosum. Edema of the complete corpus callosum has been described to be an unfavorable prognostic factor. We present an acute onset of MBD with diffusion restriction of the complete corpus callosum and symmetric bilateral extension into the semioval center, that almost completely resolved clinically as well as in MRI only 3 days later. With early detection and treatment, the prognosis of MBD may be good even in cases with severe diffusion restriction of the complete corpus callosum.

Perfusion patterns in migraine with aura

Objectives Migraine with aura is a common neurological disorder, and differentiation from transient ischemic attack or stroke based on clinical symptoms may be difficult. Methods From an MRI report database we identified 33 patients with migraine with aura and compared these to 33 age-matched ischemic stroke patients regarding perfusion patterns on perfusion-weighted imaging (PWI)-derived maps: time to peak (TTP), mean transit time (MTT), and cerebral blood flow and volume (CBF, CBV). Results In 18/33 (54.5%) patients with migraine with aura, TTP showed areas of hypoperfusion, most of these not limited to the territory of a specific artery but affecting two or more vascular territories. In patients with migraine with aura, TTP (1.09 ± 0.05 vs. 1.47 ± 0.40, p < 0.001) and MTT ratios (1.01 ± 0.10 vs. 1.19 ± 0.21, p = 0.003) were significantly lower compared to patients with ischemic stroke. In contrast to this, CBF and CBV ratios did not differ significantly between both groups. Conclusions Migraine aura is usually associated with a perfusion deficit not limited to a specific vascular territory, and only a moderate increase of TTP. Thus, hypoperfusion restricted to a single vascular territory in combination with a marked increase of TTP or MTT may be regarded as atypical for migraine aura and suggestive of acute ischemic stroke.

Diffusion- and perfusion-weighted imaging in acute lacunar infarction: is there a mismatch?

Purpose Characterization of lacunar infarction (LI) by use of multimodal MRI including diffusion- and perfusion-weighted imaging (DWI, PWI) is difficult because of the small lesion size. Only a few studies evaluated PWI in LI and the results are inconsistent. Methods In 16 LI patients who underwent initial MRI within 6 hours after symptom onset and follow-up MRI within 1 week demographics, clinical presentation, and MRI findings were analyzed with special emphasis on DWI and PWI findings. Time to peak maps were classified as showing a normal perfusion pattern or areas of hypoperfusion which were further categorized in mismatch (PWI>DWI), inverse mismatch (PWI<DWI), and match (PWI=DWI). Quantitative perfusion maps were generated and analyzed by use of Signal Processing in NMR-Software (SPIN). Results Of the 16 patients (mean age 65.5±12.9 years), 14 (87.5%) were male. Clinical symptoms comprised dysarthria (50%), hemiparesis (81.3%), and hemihypaesthesia (18.8%). Intravenous thrombolysis was performed in 7 (43.8%) patients. Clinical improvement was observed in 12 patients (75 %), while 2 (12.5%) patients showed a deterioration and another 2 (12.5%) a stable course. Acute ischemic lesions (mean volume of 0.46±0.29 cm3) were located in the thalamus (n=8, 50%), internal capsule (n=4, 25%), corona Radiata (n=3, 18.8%) and the mesencephalon (n=1, 6.3%). Circumscribed hypoperfusion (mean volume 0.61±0.48 cm3) was evident in 10 (62.5%) patients. Of these, 3 patients demonstrated a match, 4 an inverse mismatch, and 3 a mismatch between DWI and PWI lesion. Mean CBF and CBV ratios were 0.65±0.28 and 0.84±0.41 respectively. Growth of DWI lesions was observed in 7 (43.8%) and reversal of DWI lesions in 3 (18.8%) patients. Conclusions MRI allows identification of different DWI and PWI patterns in LI, including growth and reversal of ischemic lesions. Consequently, it may serve for a better characterization of this stroke subtype and support treatment decisions in daily clinical practice.

Anatomical variations in the posterior part of the circle of willis and vascular pathology in bilateral thalamic infarction.

Bilateral paramedian thalamic infarction is a rare subtype of stroke the etiology of which still remains undetermined in many patients.

Fluid Attenuated Inversion Recovery Vascular Hyperintensities Possibly Indicate Slow Arterial Blood Flow in Vertebrobasilar Dolichoectasia

Vertebrobasilar dolichoectasia (VBD) is a dilatative arteriopathy associated with a decreased blood flow velocity. Fluid attenuated inversion recovery (FLAIR) vascular hyperintensity (FVH) is a phenomenon most likely representing slow arterial blood flow. We sought to examine the frequency and extent of FVH in VBD.

Impairment of Dynamic Pressure Autoregulation Precedes Clinical Deterioration after Aneurysmal Subarachnoid Hemorrhage

This study was designed to evaluate the potential of the dynamic autoregulation index (ARI) to serve as an early warning system for an imminent clinical deterioration after subarachnoid hemorrhage (SAH).

Perfusion-weighted imaging and dynamic 4D angiograms for the estimation of collateral blood flow in lacunar infarction.

Although lacunar infarction accounts for approximately 25% of ischemic strokes, collateral blood flow through anastomoses is not well evaluated in lacunar infarction. In 111 lacunar infarction patients, we analyzed diffusion-weighted images, perfusion-weighted images, and blood flow on dynamic four-dimensional angiograms generated by use of Signal Processing In NMR-Software. Blood flow was classified as absent (type 1), from periphery to center (type 2), from center to periphery (type 3), and combination of type 2 and 3 (type 4). On diffusion-weighted images, lacunar infarction was found in the basal ganglia (11.7%), internal capsule (24.3%), corona radiata (30.6%), thalamus (24.3%), and brainstem (9.0%). In 58 (52.2%) patients, perfusion-weighted image showed a circumscribed hypoperfusion, in one (0.9%) a circumscribed hyperperfusion, whereas the remainder was normal. In 36 (62.1%) patients, a larger perfusion deficit (>7 mm) was observed. In these, blood flow was classified type 1 in four (11.1%), 2 in 17 (47.2%), 3 in 9 (25.0%), and 4 in six (16.7%) patients. Patients with lacunar infarction in the posterior circulation more often demonstrated blood flow type 2 and less often type 3 (p = 0.01). Detailed examination and graduation of blood flow in lacunar infarction by use of dynamic four-dimensional angiograms is feasible and may serve for a better characterization of this stroke subtype.

Hyperintense Acute Reperfusion Marker on FLAIR in a Patient with Transient Ischemic Attack.

The hyperintense acute reperfusion marker (HARM) has initially been described in acute ischemic stroke. The phenomenon is caused by blood-brain barrier disruption following acute reperfusion and consecutive delayed gadolinium enhancement in the subarachnoid space on fluid attenuated inversion recovery (FLAIR) images. Here we report the case of an 80-year-old man who presented with transient paresis and sensory loss in the right arm. Initial routine stroke MRI including diffusion- and perfusion-weighted imaging demonstrated no acute pathology. Follow-up MRI after three hours demonstrated subarachnoid gadolinium enhancement in the left middle cerebral artery territory consistent with HARM that completely resolved on follow-up MRI three days later. This case illustrates that even in transient ischemic attack patients disturbances of the blood-brain barrier may be present which significantly exceed the extent of acute ischemic lesions on diffusion-weighted imaging. Inclusion of FLAIR images with delayed acquisition after intravenous contrast agent application in MRI stroke protocols might facilitate the diagnosis of a recent acute ischemic stroke.

Immediate Titanium Mesh Implantation for Patients with Postcraniotomy Neurosurgical Site Infections: Safe and Aesthetic Alternative Procedure?

BACKGROUND Surgical site infection (SSI) is one of the main complications after craniotomy. The incidence is up to 11% in the literature. The established procedure is debridement, removal of the bone flap, and delayed cranioplasty. Delayed cranioplasty has several disadvantages. A promising approach is the immediate titanium mesh implantation at the time of wound revision. We report our experience with this technique regarding outcome measured by reinfection rates and patient satisfaction. METHODS Patients treated in our department from January 2013 to October 2014 with SSI after craniotomy for brain tumor, trauma, or vascular pathologies were prospectively collected. In all these patients, immediate titanium mesh implantation after bone flap removal was performed. Primary outcome parameters were the reinfection rate and patient satisfaction via self-designed questionnaires in a follow-up period >3 months. RESULTS Twenty-four patients were included within the study period. Main risk factors causing SSI were previous steroid medication (62.5%), cranial radiation therapy (42%), cerebrospinal fluid fistula after initial surgery (12.5%), and diabetes mellitus (25%). The follow-up was >3 months after titanium mesh cranioplasty (mean 4.6 months; range 3-6 months). No recurrent infection was detected in the study group. In 2 cases, reoperation was necessary. The returning questionnaires showed a high satisfaction rate with the cosmetic result. CONCLUSIONS Our small series seems to confirm that immediate titanium mesh implantation for patients with postcraniotomy SSI is a cost-effective, safe, and cosmetically suitable alternative to delayed cranioplasty in selected patients without hydrocephalus or persistent cerebrospinal fluid fistula.