Magnetic resonance elastography with guided pressure waves.

Magnetic resonance elastography aims to non-invasively and remotely characterize the mechanical properties of living tissues. To quantitatively and regionally map the shear viscoelastic moduli in vivo, the technique must achieve proper mechanical excitation throughout the targeted tissues. Although it is straightforward, ante manibus, in close organs such as the liver or the breast, which practitioners clinically palpate already, it is somewhat fortunately highly challenging to trick the natural protective barriers of remote organs such as the brain. So far, mechanical waves have been induced in the latter by shaking the surrounding cranial bones. Here, the skull was circumvented by guiding pressure waves inside the subject's buccal cavity so mechanical waves could propagate from within through the brainstem up to the brain. Repeatable, reproducible and robust displacement fields were recorded in phantoms and in vivo by magnetic resonance elastography with guided pressure waves such that quantitative mechanical outcomes were extracted in the human brain.

Prospective Follow-up of Intramedullary Slitlike Cavities: A Consecutive Series of 48 Patients.

Object: Predicting whether intramedullary slitlike cavity (SC) will worsen over time or remain stable is an outstanding clinical challenge. The aim of this study was to identify early features of SC (clinical and magnetic resonance imaging [MRI] findings). Methods: We prospectively included all patients referred to our institution following the discovery of a SC and divided them in two groups: typical SC (defined as a cavity spanning fewer than three vertebrae, not enlarging the spinal cord, and located at the midline between the anterior third and posterior two-thirds of the spinal cord) or atypical SC (all others). Clinical evolution and changes in MRI features were evaluated during follow-up. In some patients, diffusion tensor imaging was performed and cervical cord cross-sectional area was analyzed. Results: A total of 48 consecutive patients were included in the study. The mean follow-up was 58 months. Of the seven patients presenting with deficits at first consultation, two worsened and five remained stable. Of the 41 patients without deficits, seven worsened and 34 remained stable. None of the patients developed severe motor deficits or experienced enlargement of the cavity; 7% of patients who presented with typical SC worsened compared with 35% with atypical SC. The negative predictive value was 0.93 (P = 0.02). Conclusion: Most patients remained stable and a subset of patients developed minor motor deficits. For clinical management, we propose surveillance of patients with a typical SC and close follow-up of those with an atypical SC and/or presenting with deficits.

Smaller hippocampal volumes predict lower antidepressant response/remission rates in depressed patients: A meta-analysis.

OBJECTIVES: Whether hippocampal volume predicts response and/or remission after antidepressant treatment of major depressive episodes (MDE) in major depressive disorder (MDD) remains unclear. We meta-analysed prospective studies comparing baseline hippocampal volume in patients with or without response/remission after antidepressant treatment. METHODS: Pubmed, Embase and Google Scholar were searched for studies of patients with current MDE in MDD, with hippocampal volume assessments at baseline, initiation of antidepressant drug treatment, and prospective assessment of response/remission after treatment. RESULTS: Six studies (374 patients), of which two were positive and four negative, were meta-analysed. Compared to responders/remitters, patients who failed to achieve response/remission had smaller total hippocampus volumes at baseline (mean volume difference = 260 mm3, 95% CI [93; 427], P = 0.002). These results remained significant in patients under 60 years of age (P = 0.02), in those over 60 years old (P = 0.04), and for right (P = 0.006) and left (P = 0.02) hippocampi. The probability of non-response/non-remission was 68.6% for patients with a total hippocampal volume at least 10% lower than the average, and 47.1% for patients with a total hippocampal volume 10% higher than the average. CONCLUSIONS: In depressed patients treated with antidepressant drugs, smaller hippocampal volumes predict lower response/remission rates.

[Techniques and progress in the imaging of the ear]. / Les techniques et avancées dans l'imagerie de l'oreille.

Ear and temporal bone imaging is essential for the diagnostic and preoperative management of middle ear lesions. The scanner is the exam of choice to analyze the walls and the contents of the middle ear. MRI is used to characterize the opacities of the middle ear and to evaluate possible neurological complications. Modern imaging techniques allow intraoperative guidance in otological surgery. Hearing implants are not always a contraindication to MRI but require precautions according to the type of implant.

Early life adversity is associated with a smaller hippocampus in male but not female depressed in-patients: a case-control study.

BACKGROUND: Three studies assessed the association of early life adversity (ELA) and hippocampal volumes in depressed patients, of which one was negative and the two others did not control for several potential confounding variables. Since the association of ELA and hippocampal volumes differ in male and female healthy volunteers, we investigated the association of ELA and hippocampal volumes in depressed patients, while focusing specifically on sex and controlling for several relevant socio-demographic and clinical variables. METHODS: Sixty-three depressed in-patients treated in a psychiatric setting, with a current Major Depressive Episode (MDE) and a Major Depressive Disorder (MDD) were included and assessed for ELA. Hippocampal volumes were measured with brain magnetic resonance imaging (MRI) and automatic segmentation. They were compared between patients with (n = 28) or without (n = 35) ELA. After bivariate analyses, multivariate regression analyses tested the interaction of sex and ELA on hippocampal volume and were adjusted for several potential confounding variables. The subgroups of men (n = 26) and women (n = 37) were assessed separately. RESULTS: Patients with ELA had a smaller hippocampus than those without ELA (4.65 (±1.11) cm3 versus 5.25 (±1.01) cm3), bivariate: p = 0.03, multivariate: HR = 0.40, 95%CI [0.23;0.71], p = 0.002), independently from other factors. This association was found in men (4.43 (±1.22) versus 5.67 (±0.77) cm3), bivariate: p = 0.006, multivariate HR = 0.23, 95%CI [0.06;0.82], p = 0.03) but not in women. CONCLUSION: ELA is associated with a smaller hippocampus in male but not female depressed in-patients. The reasons for this association should be investigated in further studies.

Functional and structural microanatomy of the fetal sciatic nerve.

INTRODUCTION: The ultrastructure of a nerve has implications for surgical nerve repair. The aim of our study was to characterize the fascicular versus fibrillar anatomy and the autonomic versus somatic nature of the fetal sciatic nerve (SN). METHODS: Immunohistochemistry for vesicular acetylcholine transporter, tyrosine hydroxylase, and peripheral myelin protein 22 was performed to identify cholinergic, adrenergic, and somatic axons, respectively, in the human fetal SN. Two-dimensional (2D) analysis and 3D reconstructions were performed. RESULTS: The fetal SN is composed of one-third stromal tissue and two-thirds neural tissue. Autonomic fibers are predominant over somatic fibers within the neural tissue. The distribution of somatic fibers is initially random, but then become topographically organized after intra- and interfascicular rearrangements have occurred within the nerve. CONCLUSIONS: The fetal model presents limitations but enables illustration of the nature of the nerve fibers and the 3D fascicular anatomy of the SN. Muscle Nerve 56: 787-796, 2017.

Hippocampal volume predicts antidepressant efficacy in depressed patients without incomplete hippocampal inversion.

BACKGROUND: Incomplete hippocampal inversion (IHI), also called malrotation, is a frequent atypical anatomical pattern of the hippocampus. Because of the crucial implication of the hippocampus in Major Depressive Disorder (MDD) and the neurodevelopmental hypothesis of MDD, we aimed to assess the prevalence of IHI in patients with MDD, the link of IHI with hippocampal volume (HV) and the impact of IHI on the predictive value of HV for response and remission after antidepressant treatment. METHODS: IHI (right and left, partial and total and IHI scores) and HV were assessed in 60 patients with a current Major Depressive Episode (MDE) in a context of MDD and 60 matched controls. Patients were prospectively assessed at baseline and after one, three and six months of antidepressant treatment for response and remission. RESULTS: The prevalence of IHI did not significantly differ between MDD patients (right = 23.3%; left = 38.3%) and controls (right = 16.7%; left = 33.3%). IHI was not significantly associated with MDD clinical characteristics. IHI alone did not predict response and remission after antidepressant treatment. However, an interaction between left HV and left IHI predicted six-month response (p = 0.04), HDRS score decrease (p = 0.02) and both three-month (p = 0.04) and six-month (p = 0.03) remission. A case-control design in 30 matched patients with or without left IHI confirmed that interaction. In patients without left IHI, left HV at baseline were smaller in six-month non-remitters as compared to remitters (2.2(± 0.43) cm3 vs 2.97(± 0.5) cm3 p = 0.02), and in six-month non-responders as compared to responders (2.18(± 0.42) cm3 vs 2.86(± 0.54) cm3, p = 0.03). In patients with left IHI, no association was found between left HV at baseline and antidepressant response and remission. CONCLUSION: IHI is not more frequent in MDD patients than in controls, is not associated with HV, but is a confounder that decreases the predictive value of hippocampal volume to predict response or remission after antidepressant treatment. IHI should be systematically assessed in future research studies assessing hippocampal volume in MDD.

Diffusion tensor magnetic resonance imaging of trigeminal nerves in relapsing herpetic keratouveitis.

BACKGROUND: Corneal hypoesthesia is the landmark of HSV and VZV keratitis and can lead to neurotrophic keratitis. Diffusion tensor imaging (DTI) is a new magnetic resonance imaging (MRI) derived technique, which offers possibilities to study axonal architecture. We aimed at assessing the potential impact of recurrent HSV or VZV-related keratitis on the axonal architecture of trigeminal nerves using DTI. DESIGN: Prospective non-interventional study. PARTICIPANTS: Twelve patients and 24 controls. METHODS: DTI using MRI of the trigeminal fibers and corneal esthesiometry using the Cochet-Bonnet esthesiometer were acquired for patients affected by unilateral and recurrent HSV or VZV-related keratitis (3 months after the last corneal inflammatory event), and control subjects with no history of ocular or neuronal disease affecting the trigeminal pathways. MAIN OUTCOME MEASURES: Fractional anisotropy (FA) and apparent diffusion coefficient (ADC) were compared between the 2 eyes of both patients and controls, and correlated with corneal esthesiometry. RESULTS: FA was lower in the trigeminal fibers ipsilateral to the affected eye compared to the non-affected side (0.39±0.02 versus 0.46±0.04, P=0.03). This difference was more important than the intra-individual variability observed in controls. Concomitantly, the asymmetry in ADC results was significantly correlated with the loss of corneal sensitivity in the affected eye. CONCLUSIONS: Corneal hypoesthesia related to HSV and VZV keratitis is associated with persistent modifications in the architecture and functionality of the trigeminal fibers. These results add further explanation to the pathogenesis of HSV and VZV-induced neurotrophic keratitis, which may occur despite an apparent quiescence of the disease.

Extracranial vertebral artery dissection in children: natural history and management.

INTRODUCTION: The objective of this study is to describe clinical and imaging presentation and outcome in extracranial vertebral artery dissection. METHODS: Single-centre retrospective study over a 14-year period included 20 consecutive patients under the age of 16 years with extracranial vertebral artery dissection. The diagnosis was based on vascular imaging performed at the acute phase and clinical symptoms. RESULTS: A male predominance was observed (sex ratio 9/1). The first symptoms consisted of headache (45%), neck pain (15%), nausea (30%) and vertigo (30%). Clinical signs leading to admission to hospital were hemiparesis (60%), visual disorders with oculomotor disorders (20%) or visual field defects (20%) and cerebellar syndrome (35%). Eight patients (40%) reported repeated transient episodes of neurological deficits, prior to the diagnosis. The segment most commonly affected was V2-V3 (50%), followed by V3 (15%) and V2 (15%), V3-V4 (10%) and proximal V4 (10%). All patients but one presented cerebral infarction. Eleven patients received first-line treatment with low molecular weight heparin (LMWH), and nine patients received aspirin. Three patients experienced a recurrence of symptoms, one under vitamin K antagonist (VKA) and 2 under aspirin. All three were switched to LMWH with success. Fifty-eight percent of the dissected arteries were occluded at long-term follow-up, although 73% of them were patent at the acute phase. CONCLUSION: Initial imaging must include posterior fossa vessels and the craniocervical region with V2-V3 segments. Conventional angiography may be indicated in the absence of a definitive diagnosis on noninvasive imaging. Healing of the dissected vertebral artery predominantly resulted in occlusion, which does not constitute a pejorative factor but indicates good quality healing.

Depressed suicide attempters have smaller hippocampus than depressed patients without suicide attempts.

BACKGROUND: Despite known relationship between hippocampal volumes and major depressive episodes (MDE) and the increased suicidality in MDE, the links between hippocampal volumes and suicidality remain unclear in major depressive disorders (MDD). If the hippocampus could be a biomarker of suicide attempts in depression, it could be useful for prevention matters. This study assessed the association between hippocampal volumes and suicide attempts in MDD. METHODS: Hippocampal volumes assessed with automatic segmentation were compared in 63 patients with MDD, with (n = 24) or without (n = 39) suicide attempts. Acute (one month) suicide attempts were studied. RESULTS: Although not different in terms of socio-demographic, MDD and MDE clinical features, suicide attempters had lower total hippocampus volumes than non-attempters (4.61 (± 1.15) cm(3) vs 5.22 (± 0.99) cm(3); w = 625.5; p = 0.03), especially for acute suicide attempts (4.19 (± 0.81) cm(3) vs 5.22 (± 0.99) cm(3); w = 334; p = 0.005), even after adjustment on brain volumes, sex, age, Hamilton Depression Rating Scale (HDRS) scores and MDD duration. A ROC analysis showed that a total hippocampal volume threshold of 5.00 cm(3) had a 98.2% negative predictive value for acute suicide attempts. CONCLUSION: Depressed suicide attempters have smaller hippocampus than depressed patients without suicide attempts, independently from socio-demographics and MDD characteristics. This difference is related to acute suicide attempts but neither to past suicide attempts nor to duration since the first suicide attempt, suggesting that hippocampal volume could be a suicidal state marker in MDE. Further studies are required to better understand this association.

Statistical analysis of multi-b factor diffusion weighted images can help distinguish between vasogenic and tumor-infiltrated edema.

PURPOSE: The diffusion model can be transformed into a multicompartment model by means of multi-b factor diffusion-weighted sequences. We adapted a method of statistical analysis of these images and evaluated its performance to distinguish tumor-infiltrated edema from vasogenic edema. MATERIALS AND METHODS: Forty-nine patients with infiltrating tumors (38 patients: low to high-grade gliomas) or vasogenic edema (11 patients: metastases, abscess, extra-axial lesions) were studied by multi-b factor diffusion-weighted imaging. Comparison of histological results and morphological and perfusion MRI defined 69 characteristic volumes of interest in the peritumoral edema of 69 distinct infiltrating lesions (40) or lesions inducing vasogenic edema (29). RESULTS: The factorial analysis had a sensitivity of 92.9% and a specificity of 90.6% between tumor-infiltrated and vasogenic edema. Simplified interpretation confined to values of the high and mean diffusivity compartments had a sensitivity of 87.5% and a specificity of 89.2% between strictly tumor-infiltrated edema and vasogenic edema with the advantage of simplified interpretation based on two-color parametric mapping. CONCLUSION: Discrimination between tumor-infiltrated edema and vasogenic edema can be achieved by means of a 90-s multi-b factor diffusion-weighted sequence and factorial analysis. Simplified visual and quantitative interpretation of the results should also allow integration of multi-b factor analysis into routine neuroradiology practice.

Computed tomography of the anterior skull base in Kallmann syndrome reveals specific ethmoid bone abnormalities associated with olfactory bulb defects.

CONTEXT: Kallmann syndrome (KS) is characterized by congenital hypogonadotropic hypogonadism (CHH) and an impaired sense of smell related to defective development of the olfactory system. OBJECTIVE: The aim of the study was to use high-resolution computed tomography (CT) to detect specific abnormalities in the ethmoid bone region surrounding the olfactory bulbs in patients with KS. PATIENTS: Thirty-seven KS patients were compared to normosmic CHH (nCHH) patients (n = 15) and controls (n = 30) of similar age. DESIGN AND METHODS: We conducted a prospective study in a single referral center. Subjects underwent CT in bone windows with axial, coronal, and sagittal reconstructions centered on the olfactory fossa (OF) and cribriform plate (CP). We characterized the OF structure by measuring OF height, width, and surface area and a series of angles. The CP foramina were counted bilaterally. Olfactory bulb magnetic resonance imaging, performed in parallel, was compared with CT findings. RESULTS: OF height, width, and surface area were all significantly lower in KS patients than in nCHH patients and controls (P < .0001). KS patients also had wider angles than nCHH patients and controls (P < .0001). KS subjects with olfactory bulb agenesis on magnetic resonance imaging or who harbored KAL1 mutations had the most marked changes in OF measurements and angles. Coronal OF height distinguished KS patients from controls with the best sensitivity and specificity. The mean number of CP foramina was similar in KS, nCHH, and control subjects. CONCLUSIONS: KS is associated with specific ethmoid bone abnormalities. The preserved number of CP foramina in KS patients suggests that the integrity of olfactory structures is not mandatory for their formation during fetal development or their maintenance in adult life.

A correlation between fractional anisotropy variations and clinical recovery in spinal cord infarctions.

PURPOSE: To describe diffusion-weighted imaging and diffusion tensor imaging variations in spinal cord infarctions. METHODS: We studied the apparent diffusion coefficient (ADC) and fractional anisotropy (FA) local variations in 2 patients with spinal cord infarcts in the conus region at days 3-4, 9-10, and 15-22 after clinical onset, and correlated them with the clinical outcome. RESULTS: Both patients (19 and 53 years-old) presented spinal cord infarction unraveled by paraparesis and bladder dysfunction. Although initial clinical and radiological presentations were similar, the first patient early and fully recovered whereas the second kept severe bladder dysfunctions. Early absolute values of FA and ADC did not seem to correlate with outcome. At day 9-10, the second patient, who presented definitive sequel, had decreasing values of FA in the ischemic region whereas they had increased in the first patient, who fully recovered. CONCLUSION: FA values could be an interesting prognosis marker in spinal cord ischemia, which needs to be confirmed by a larger study.

Cortical border-zone infarcts: clinical features, causes and outcome.

OBJECTIVE: To report the clinical features, causes and outcome of cerebral cortical border-zone infarcts BZI (C-BZI). METHODS: The authors prospectively included patients with MRI-confirmed C-BZI among individuals consecutively admitted in Stroke Unit. RESULTS: Forty-five patients presented C-BZI out of 589 with MRI-confirmed cerebral infarcts (7.6%). Particular clinical characteristics existed in C-BZI in comparison with other cerebral infarctions as a whole, including: (1) frequent transient symptoms at onset (27% vs 9%; p<0.001) and low severity score (NIHSS=3.1±3.0 vs 5.2±6.1; p=0.02); (2) early seizures in first 2 weeks (7/45 (15.6%) vs 12/544 (2.2%); p<0.001), even when focusing only on other infarctions involving the cerebral cortex (15.6% vs 4.3%; p<0.01); (3) heterogeneous clinical presentation but specific transcortical aphasia allowing a clinical suspicion of BZI before MRI; and (4) frequently associated internal carotid disease (69%), with subsequent early surgery in 75% of the cases. Following adapted care in stroke unit, C-BZIs' prognosis appeared good (Rankin score ≤2 at D90) for 82% of the patients. CONCLUSION: Some clinical features are overrepresented in such infarctions, including initial transient symptoms preceding the onset of a completed deficit, transcortical aphasia and early seizures. Despite lower initial severity, C-BZIs justify early management in stroke unit, often followed by carotid surgery, leading to an overall good prognosis.

Diffusion tensor imaging tractography parameters of limbic system bundles in temporal lobe epilepsy patients.

PURPOSE: To investigate changes in diffusion tensor imaging (DTI) measures in limbic system white matter of patients with temporal lobe epilepsy (TLE) using diffusion tensor tractography. MATERIALS AND METHODS: DTI metrics including fractional anisotropy (FA), λ1, λ2, λ3, and trace (Tr) coefficients were obtained from tractography for bilateral fornix, superior and inferior cingulum fibers in 18 patients and 10 healthy controls. Hippocampal signal-to-noise ratio (SNR) quantitative analysis was performed in order to confirm the magnetic resonance imaging (MRI) hippocampal lesion presence or absence in TLE patients. RESULTS: Nine patients presented unilateral hippocampal sclerosis (TLE+HS) and nine patients had no signal abnormalities on conventional MRI (TLE-HS). On the ipsilateral seizure side, all three investigated tracts showed significant DTI indices abnormalities in both patient groups when compared with controls, most marked on the inferior cingulum. Contralateral to the seizure side, the three tracts presented significant DTI parameters in only the TLE+HS group when compared with controls. CONCLUSION: The DTI abnormalities found in the TLE-HS group may suggest that in the inferior cingulum the structural integrity is more affected than in the fornix or superior cingulum white matter bundles. The eigenvalues taken separately add complementary information to the FA and Tr metrics and may be useful indices in better understanding the architectural reorganization of limbic system tracts in TLE patients without HS.

Congenital vertebral duplication: a predisposing risk factor for dissection.

Spontaneous cervical-artery dissection (CAD) is a major cause of cerebral ischaemia in young adults. While their pathophysiology remains still poorly understood, CAD is considered today as a multifactorial disease determined by general and local predisposing factors; these predisposing factors being predominantly constitutional abnormalities of the arterial wall. Here, we report an MRI-confirmed dissection of a duplicated vertebral artery, in a patient with attacks of vertigo due to cerebellar infarction following a minor neck trauma. Knowing that another case of vertebrobasilar CAD on a duplicated vertebral artery has been reported, these rare anatomical variants probably predispose to vertebral CAD, via local histological defects or significant hemodynamics alterations, as reported for the classical local predisposing conditions for vertebral dissection, i.e.: fibromuscular dysplasias or carotid redundancies (including loops, kinks and coils).

Cerebral peritumoral oedema study: does a single dynamic MR sequence assessing perfusion and permeability can help to differentiate glioblastoma from metastasis?

Our purpose was to differentiate glioblastoma from metastasis using a single dynamic MR sequence to assess perfusion and permeability parameters. 24 patients with glioblastoma or cerebral metastasis with peritumoral oedema were recruited and explored with a 3T MR unit. Post processing used DPTools software. Regions of interest were drawn around contrast enhancement to assess relative cerebral blood volume and permeability parameters. Around the contrast enhancement Glioblastoma present high rCBV with modification of the permeability, metastasis present slight modified rCBV without modification of permeability. In conclusion, peritumoral T2 hypersignal exploration associating morphological MR and functional MR parameters can help to differentiate cerebral metastasis from glioblastoma.