Transient memory impairment and transient global amnesia induced by photodynamic therapy.

Photodynamic therapy (PDT) is a commonly used and effective treatment option for nonmelanoma skin cancer. Apart from local side-effects such as pain, oedema and erythema, no major adverse events occur in the majority of cases. Here we report on five patients who developed memory deficits such as transient global amnesia immediately after PDT for actinic keratosis. All PDT treatments were performed according to standard therapy protocols. The reported patients had a memory gap for the entire procedure, as well as for the consecutive emergency medical care. Other common neurological causes such as stroke or epileptic seizures were excluded. No focal neurological deficits were detectable. The symptoms had a fairly rapid onset following red-light illumination and were reversible without sequelae within 1-24 h. No correlation of the condition and pain during the illumination could be revealed. Magnetic resonance imaging of the brain revealed punctuated lesions in the hippocampus as a potential morphological correlate in one patient. The association between amnestic syndromes and PDT is novel and has not previously been reported. Even though PDT is considered a safe treatment modality, the possibility of neurological adverse events, albeit rare, should be kept in mind.

Prevalence of superficial siderosis following singular, acute aneurysmal subarachnoid hemorrhage.

INTRODUCTION: Superficial siderosis is presumably a consequence of recurrent bleeding into the subarachnoid space. The objective of this study was to assess the prevalence of superficial siderosis after singular, aneurysmal subarachnoid hemorrhage (SAH) in the long term. METHODS: We retrospectively identified all patients who presented with a singular, acute, aneurysmal SAH at our institution between 2010 and 2013 and in whom a magnetic resonance imaging (MRI) including T2*-weighted imaging was available at least 4 months after the acute bleeding event. MRI scans were judged concerning the presence and distribution of superficial siderosis. Influence of clinical data, Fisher grade, localization, and cause of SAH as well as the impact of neurosurgical interventions on the occurrence of superficial siderosis was tested. RESULTS: Seventy-two patients with a total of 117 MRIs were included. Mean delay between SAH and the last available MRI was 47.4 months (range 4-129). SAH was Fisher grade 1 in 2 cases, 2 in 4 cases, 3 in 10 cases, and 4 in 56 cases. Superficial siderosis was detected in 39 patients (54.2%). In all patients with more than one MRI scan, localization and distribution of superficial siderosis did not change over time. Older age (p = 0.02) and higher degree of SAH (p = 0.03) were significantly associated with the development of superficial siderosis. CONCLUSION: Superficial siderosis develops in approximately half of patients after singular, aneurysmal SAH and might be more common in patients with an older age and a greater amount of blood. However, additional factors must play a role in whether a patient is prone to develop superficial siderosis or not.

Diffusion tensor imaging of the trigeminal nerve in patients with trigeminal neuralgia due to multiple sclerosis.

INTRODUCTION: Neurovascular compression (NVC) is the most common cause of trigeminal neuralgia (TN), leading to microstructural changes in the affected nerve detectable using diffusion tensor imaging (DTI). But TN may also emerge as a symptom of multiple sclerosis (MS). The aim of this study was to evaluate if patients with MS-related TN feature the same DTI characteristics as patients with TN caused by NVC. METHODS: Twelve patients with MS-related TN, 12 age-matched patients with NVC-related TN, and 12 healthy controls were included. Using 3T-DTI, mean fractional anisotropy (FA) and apparent diffusion coefficient (ADC) values were calculated for each affected and contralateral trigeminal nerve in patients with MS and NVC-related TN as well as healthy controls. Furthermore, presence of NVC was evaluated for patients with TN. RESULTS: There was no significant difference concerning FA or ADC when comparing the affected and the non-affected sides in patients with MS. FA was significantly lower and ADC higher in patients with MS on the TN affected as well as on the non-affected side compared to the non-affected side of patients with idiopathic TN or healthy controls. Likewise, FA was significantly lower on the affected side compared to the non-affected side in patients with idiopathic TN or healthy controls. NVC was evident in 41.7/0% on the affected/contralateral side in MS patients and 100/8% in the patients with NVC-related TN. CONCLUSION: In patients with MS-related TN, DTI reveals microstructural changes within the trigeminal nerve not only on the affected side but also on the clinically non-affected side.

Time-of-flight angiography: a viable alternative to contrast-enhanced MR angiography and fat-suppressed T1w images for the diagnosis of cervical artery dissection?

OBJECTIVES: To compare the use of an unenhanced high-resolution time-of-flight MR angiography sequence (Hr-TOF MRA) with fat-suppressed axial/coronal T1-weighted images and contrast-enhanced angiography (standard MRI) for the diagnosis of cervical artery dissection (cDISS). METHODS: Twenty consecutive patients (9 women, 11 men, aged 24-66 years) with proven cDISS on standard MRI underwent Hr-TOF MRA at 3.0 T using dedicated surface coils. Sensitivity (SE), specificity (SP), positive and negative predictive values (PPV, NPV), Cohen's kappa (к) and accuracy of Hr-TOF MRA were calculated using the standard protocol as the gold standard. Image quality and diagnostic confidence were assessed on a four-point scale. RESULTS: Image quality was rated better for standard MRI (P = 0.02), whereas diagnostic confidence did not differ significantly (P = 0.27). There was good agreement between Hr-TOF images and the standard protocol for the presence/absence of cDISS, with к = 0.95 for reader 1 and к = 0.89 for reader 2 (P < 0.001). This resulted in SE, SP, PPV, NPV and accuracy of 97 %, 98 %, 97 %, 98 % and 97 % for reader 1 and 93 %, 96 %, 93 %, 96 % and 95 % for reader 2. CONCLUSIONS: Hr-TOF MRA can be used to diagnose cDISS with excellent agreement compared with the standard protocol. This might be useful in patients with renal insufficiency or if contrast-enhanced MR angiography is of insufficient image quality. KEY POINTS: • New magnetic resonance angiography sequences are increasingly used for vertebral artery assessment. • A high-resolution time-of-flight sequence allows the diagnosis of cervical artery dissection. • This technique allows the diagnosis without intravenous contrast medium. • It could help in renal insufficiency or when contrast-enhanced MRA fails.

Magnetic Resonance Imaging Characteristics of Retinal Vasculopathy with Cerebral Leukoencephalopathy and Systemic Manifestations.

BACKGROUND: Retinal vasculopathy with cerebral leukoencephalopathy and systemic manifestations (RVCL-S) is a rare hereditary disease presenting with distinct imaging features in middle-aged adults. This article describes the typical imaging features focusing on the longitudinal course of RVCL-S lesions. METHODS: In this study six subjects (five male, five related) with RVCL-S were retrospectively included from two university hospitals. The median age of symptom onset was 40 ± 6 years. Magnetic resonance imaging (MRI) covering baseline and a median follow-up period of 33 months was reviewed in a structured way focusing on morphology, contrast enhancement and diffusion restriction of brain lesions. RESULTS: All patients showed patchy, T2 hyperintense white matter lesions (mean number 7.7 ± 1.8) with a periventricular predominance at the frontal lobes (59%). In all subjects, rim-enhancing white matter lesions with temporary diffusion restriction were present for a mean of 5.0 ± 3.9 months. Median duration of blood brain barrier disruption was 20 months. CONCLUSION: Periventricular patchy white matter lesions in the frontal lobes as well as rim-enhancing lesions with prolonged diffusion restriction and long-lasting contrast enhancement are characteristic imaging findings in RCVL-S and can be helpful in the differential diagnosis.

Spectrum and Prevalence of Pathological Intracranial Magnetic Resonance Imaging Findings in Acute Bacterial Meningitis.

PURPOSE: Aim of this study was to determine the spectrum and prevalence of pathological intracranial magnetic resonance imaging (MRI) findings in patients with acute bacterial meningitis. METHODS: We retrospectively identified all consecutive patients with cerebral spinal fluid proven bacterial meningitis who presented at our neurology department between 2007 and 2012. Pathogenic agents and clinical symptoms were noted. MR-examinations were evaluated regarding presence and localization of pathological signal alterations in the different sequences by two neuroradiologists in consensus. RESULTS: A total of 136 patients with purulent bacterial meningitis were identified. In 114 cases the bacterial pathogen agent was proven and in 75 patients an MRI was available. In 62 of the 75 (82.7 %) patients meningitis-associated pathologic imaging findings were evident on MRI. Overall, intraventricular signal alterations, i.e., signs of pyogenic ventriculitis, were present in 41 cases (54.7 %), while sulcal signal changes were found in 22 cases (29.3 %). Intraparenchymatous signal alterations affected the cortex in 15 cases (20 %), and the white matter in 20 patients (26.7 %). The diffusion-weighted imaging and fluid attenuated inversion recovery sequences were most sensitive in the detection of these changes and showed any pathologic findings in 67.6 and 79.6 %, respectively. Patients with streptococcal meningitis showed significantly more often (n = 29 of 34, 85.3 %) intraventricular and/or sulcal diffusion restrictions than patients with meningitis caused by other agents (n = 12 of 37, 32.4 %) (p< 0.0001). CONCLUSION: Pathological MR findings are frequently found in patients with acute bacterial meningitis. Intraventricular diffusion restrictions, i.e., signs of pyogenic ventriculitis, are more often found in patients with streptococcal, especially pneumococcal, infection.

Hyperattenuated intracerebral lesions after mechanical recanalization in acute stroke.

BACKGROUND AND PURPOSE: Following mechanical recanalization of an acute intracranial vessel occlusion, hyperattenuated lesions are frequently found on postinterventional cranial CT. They represent either blood or-more frequently-enhancement of contrast agent. Here, we aimed to evaluate the prognostic value of these hyperattenuated intracerebral lesions. MATERIALS AND METHODS: One hundred one consecutive patients with acute stroke in the anterior circulation who underwent mechanical recanalization were included. Risk factors for hyperattenuated intracerebral lesions were assessed, and lesion volume was compared with the volume of final infarction. Clinical outcome and relative risk of secondary hemorrhage were determined in patients with and without any hyperattenuated lesions and compared. RESULTS: The frequency of hyperattenuated lesions was 84.2%. Risk factors for hyperattenuated lesions were female sex, higher NIHSS score on admission, and higher amount of contrast agent applied. On follow-up, 3 patients showed no infarction; 53 patients, an ischemic infarction; and 45 patients, a hemorrhagic infarction. In all except 1 case, final volume of infarction (median = 92.4 mL) exceeded the volume of hyperattenuated intracerebral lesions (median = 5.6 mL). Patients with hyperattenuated lesions were at a 4 times higher relative risk for hemorrhagic transformation but had no significantly worse clinical outcome. CONCLUSIONS: Our data show that the extent of postinterventional hyperattenuated intracerebral lesions underestimates the volume of final infarction. Although hyperattenuated lesions indicate a higher risk of secondary hemorrhagic transformation, their presence seems not to be of any prognostic value regarding clinical outcome.

Susceptibility-weighted angiography (SWAN) of cerebral veins and arteries compared to TOF-MRA.

PROBLEM: High resolution, non-contrast imaging of both cerebral veins and arteries by use of gradient echo T2 star weighted angiography (SWAN) is a new method for susceptibility-weighted imaging with short acquisition times. We assessed the potential of this sequence for the depiction of both cerebral veins and arteries. METHODS: 15 healthy volunteers were included in the study. MRI was performed on a 3T MR scanner using the following sequences: (1) a 3D multi-echo gradient echo T2 star weighted angiography (SWAN), (2) an arterial 3D TOF MR angiography and (3) a venous 2D TOF. With regard to the SWAN sequence, both MinIP and MIP images were reconstructed and systematically compared to MIP reconstructions of the artTOF and the venTOF. To suggest possible clinical implications of our findings, we additionally included two illustrative cases. RESULTS: With regard to the visualization of the cerebral veins, the MinIP reconstructions of the SWAN sequence were considerably superior compared to the venTOF. Concerning the depiction of the main segments of the big cerebral arteries the value of the MIP reconstructions of the SWAN was comparable to that of the artTOF with limitations in the homogenity and in the depiction of smaller arteries. CONCLUSIONS: SWAN allows for high-resolution visualization of both cerebral veins and arteries in one sequence without application of contrast agent and with significantly shortened scan time compared to the combined scan time of TOF-MRA and TOF-MRV. By use of either MinIP or MIP reconstructions, the arteries can be distinguished from the veins.

Variability of morphology and signal intensity of alar ligaments in healthy volunteers using MR imaging.

BACKGROUND AND PURPOSE: Evaluation of alar traumatic injuries by using MR imaging is frequently performed. This study investigates the variability of morphology and signal intensity of alar ligaments in healthy volunteers so that pathology can be more accurately defined. MATERIALS AND METHODS: Fifty healthy volunteers were examined on a 1.5T MR imaging scanner with 2-mm PD-weighted sequences in 3 planes. Delineation of the alar ligaments in 3 planes and signal-intensity characteristics on sagittal planes were analyzed by using a 4-point grading scale. Variability of courses and morphologic characteristics were described. RESULTS: Delineation of alar ligaments was best viewed in the coronal plane, followed by the sagittal and axial planes. In the sagittal view, 6.5% of alar ligaments appeared homogeneously dark. Hyperintense signal intensity in up to one-third of the cross-sectional area was present in 33% of cases; in up to two-thirds of the cross-sectional area, in 45% of cases; and in more than two-thirds of the cross-sectional area, in 15% of cases. Of alar ligaments, 58.5% ascended laterally, 40.5% ran horizontally, and 1% descended laterally. The cross-sectional area was round in 41.5%, oval in 51.5%, and winglike in 6.5%. CONCLUSIONS: On 1.5T MR imaging, the alar ligaments can be delineated best in the coronal and sagittal planes. Our data indicate a remarkable variability of morphology and course as well as signal intensity. This finding is contradictory to former publications assigning such alterations exclusively to patients with trauma.

3D fluid-attenuated inversion recovery imaging: reduced CSF artifacts and enhanced sensitivity and specificity for subarachnoid hemorrhage.

BACKGROUND AND PURPOSE: FLAIR images are highly sensitive for SAH. However, CSF flow artifacts caused by conventional FLAIR can produce false-positive results. Here, we compare 3D and 3D FLAIR sequences, focusing on their potential for containing these artifacts and their sensitivity and specificity for detection of SAHs. MATERIALS AND METHODS: We evaluated the following 4 FLAIR sequences: 1) 2D FLAIR at 1.5T, 2) 2D FLAIR, 3) 2D PROPELLER-FLAIR, and 4) 3D Cube-FLAIR at 3T. All sequences were performed in 5 healthy volunteers; sequences 2 and 4 were also performed under routine conditions in 10 patients with focal epilepsy and in 10 patients with SAH. Two neuroradiologists independently conducted the analysis. The presence of flow artifacts in the ventricles and cisterns of healthy volunteers and patients with epilepsy was evaluated and scored on a 4-point scale. Mean values were calculated and compared by using paired t tests. Sensitivity and specificity for SAH detection in sequences 2 and 4 were determined. RESULTS: Cube-FLAIR showed almost no CSF artifacts in the volunteers and the patients with epilepsy; therefore, it was superior to any other FLAIR (P < .001). Sensitivity and specificity of SAH detection by 3T FLAIR were 58.3% and 89.4%, respectively, whereas Cube-FLAIR had a sensitivity of 95% and a specificity of 100%. CONCLUSIONS: Cube-FLAIR allows FLAIR imaging with almost no CSF artifacts and is, thus, particularly useful for SAH detection.

Decrease of thalamic gray matter following limb amputation.

Modern neuroscience has elucidated general mechanisms underlying the functional plasticity of the adult mammalian brain after limb deafferentation. However, little is known about possible structural alterations following amputation and chronic loss of afferent input in humans. Using voxel-based morphometry (VBM), based on high-resolution magnetic resonance images, we investigated the brain structure of 28 volunteers with unilateral limb amputation and compared them to healthy controls. Subjects with limb amputation exhibited a decrease in gray matter of the posterolateral thalamus contralateral to the side of the amputation. The thalamic gray matter differences were positively correlated with the time span after the amputation but not with the frequency or magnitude of coexisting phantom pain. Phantom limb pain was unrelated to thalamic structural variations, but was positively correlated to a decrease in brain areas related to the processing of pain. No gray matter increase was detected. The unilateral thalamic differences may reflect a structural correlate of the loss of afferent input as a secondary change following deafferentation.