Contemporary and emerging magnetic resonance imaging methods for evaluation of moyamoya disease

Numerous recent technological advances offer the potential to substantially enhance the MRI evaluation of moyamoya disease (MMD). These include high-resolution volumetric imaging, high-resolution vessel wall characterization, improved cerebral angiographic and perfusion techniques, high-field imaging, fast scanning methods, and artificial intelligence. This review discusses the current state-of-the-art MRI applications in these realms, emphasizing key imaging findings, clinical utility, and areas that will benefit from further investigation. Although these techniques may apply to imaging of a wide array of neurovascular or other neurological conditions, consideration of their application to MMD is useful given the comprehensive multidimensional MRI assessment used to evaluate MMD. These MRI techniques span from basic cross-sectional to advanced functional sequences, both qualitative and quantitative.The aim of this review was to provide a comprehensive summary and analysis of current key relevant literature of advanced MRI techniques for the evaluation of MMD with image-rich case examples. These imaging methods can aid clinical characterization, help direct treatment, assist in the evaluation of treatment response, and potentially improve the understanding of the pathophysiology of MMD.

Peripheral nerve grafts implanted into the substantia nigra in patients with Parkinson's disease during deep brain stimulation surgery: 1-year follow-up study of safety, feasibility, and clinical outcome

OBJECTIVECurrently, there is no treatment that slows or halts the progression of Parkinson's disease. Delivery of various neurotrophic factors to restore dopaminergic function has become a focus of study in an effort to fill this unmet need for patients with Parkinson's disease. Schwann cells provide a readily available source of such factors. This study presents a 12-month evaluation of safety and feasibility, as well as the clinical response, of implanting autologous peripheral nerve grafts into the substantia nigra of patients with Parkinson's disease at the time of deep brain stimulation (DBS) surgery.METHODSStandard DBS surgery targeting the subthalamic nucleus was performed in 8 study participants. After DBS lead implantation, a section of the sural nerve containing Schwann cells was harvested and unilaterally grafted to the substantia nigra. Adverse events were continually monitored. Baseline clinical data were obtained during standard preoperative evaluations. Clinical outcome data were obtained with postoperative clinical evaluations, neuropsychological testing, and MRI at 1 year after surgery.RESULTSAll 8 participants were implanted with DBS systems and grafts. Adverse event profiles were comparable to those of standard DBS surgery with the exception of 1 superficial infection at the sural nerve harvest site. Three participants also reported numbness in the distribution of the sural nerve distal to the harvest site. Motor scores on Unified Parkinson's Disease Rating Scale (UPDRS) part III while the participant was off therapy at 12 months improved from baseline (mean ± SD 25.1 ± 15.9 points at 12 months vs 32.5 ± 9.7 points at baseline). An analysis of the lateralized UPDRS scores also showed a greater overall reduction in scores on the side contralateral to the graft.CONCLUSIONSPeripheral nerve graft delivery to the substantia nigra at the time of DBS surgery is feasible and safe based on the results of this initial pilot study. Clinical outcome data from this phase I trial suggests that grafting may have some clinical benefit and certainly warrants further study to determine if this is an efficacious and neurorestorative therapy.Clinical trial registration no.: NCT01833364 (clinicaltrials.gov).

Use of magnetic resonance imaging in severe pediatric traumatic brain injury: assessment of current practice

OBJECTIVE

There is no consensus on the optimal timing and specific brain MRI sequences in the evaluation and management of severe pediatric traumatic brain injury (TBI), and information on current practices is lacking. The authors performed a survey of MRI practices among sites participating in a multicenter study of severe pediatric TBI to provide information for designing future clinical trials using MRI to assess brain injury after severe pediatric TBI.

METHODS

Information on current imaging practices and resources was collected from 27 institutions participating in the Approaches and Decisions after Pediatric TBI Trial. Multiple-choice questions addressed the percentage of patients with TBI who have MRI studies, timing of MRI, MRI sequences used to investigate TBI, as well as the magnetic field strength of MR scanners used at the participating institutions and use of standardized MRI protocols for imaging after severe pediatric TBI.

RESULTS

Overall, the reported use of MRI in pediatric patients with severe TBI at participating sites was high, with 40% of sites indicating that they obtain MRI studies in > 95% of this patient population. Differences were observed in the frequency of MRI use between US and international sites, with the US sites obtaining MRI in a higher proportion of their pediatric patients with severe TBI (94% of US vs 44% of international sites reported MRI in at least 70% of patients with severe TBI). The reported timing and composition of MRI studies was highly variable across sites. Sixty percent of sites reported typically obtaining an MRI study within the first 7 days postinjury, with the remainder of responses distributed throughout the first 30-day postinjury period. Responses indicated that MRI sequences sensitive for diffuse axonal injury and ischemia are frequently obtained in patients with TBI, whereas perfusion imaging and spectroscopy techniques are less common.

CONCLUSIONS

Results from this survey suggest that despite the lack of consensus or guidelines, MRI is commonly obtained during the acute clinical setting after severe pediatric TBI. The variation in MRI practices highlights the need for additional studies to determine the utility, optimal timing, and composition of clinical MRI studies after TBI. The information in this survey describes current clinical MRI practices in children with severe TBI and identifies important challenges and objectives that should be considered when designing future studies.

Long-term follow-up of intensive chemotherapy followed by reduced-dose and reduced-field irradiation for intracranial germ cell tumor

OBJECTIVE The authors analyzed the efficacy of intensive chemotherapy followed by reduced-dose and reduced-field irradiation for intracranial germ cell tumors (GCTs) and evaluated the long-term late effects caused by chemoradiotherapy (CRT). METHODS The authors performed a retrospective study. The subjects were 24 patients who received CRT between April 1994 and April 2015. After surgery, intensive chemotherapy followed by reduced-dose and reduced-field irradiation was administered. For those with pure germinoma, who comprised the “good prognosis” group, five courses of conventional-dose chemotherapy (CDC) were administered, and radiotherapy (24 Gy) was applied to the whole ventricle. For all others, defined as the “intermediate and poor prognosis” group, two or three courses of CDC and high-dose chemotherapy were administered with peripheral blood stem cell transplantation and radiotherapy (24–30 Gy) applied to the whole ventricle or a larger field with or without local boost irradiation (20 Gy), which was applied as needed. RESULTS The median period of follow-up was 112.5 months (range 28–261 months), and the 5-/10-year overall and progression-free survival rates were 100%/83.5% and 91.3%/86.5%, respectively. The 5-/10-year overall survival rates determined based on the histological subtypes were 100%/100% for pure germinoma and 93.8%/78.7% for others, respectively. The late toxicities were as follows: endocrine disorder (33% in pure germinoma, 56% in others), involuntary movements (17% in pure germinoma, 39% in others), ear and labyrinth disorders (17% in pure germinoma, 33% in others), and psychiatric disorders (0% in pure germinoma, 33% in others). Nineteen of 24 patients underwent MRI (T2*- or susceptibility-weighted imaging) after radiotherapy, and 16 (84%) of those 19 patients had microbleeds detected, while 2 (10.5%) had radiation-induced cavernous vascular malformations detected. CONCLUSIONS Intensive chemotherapy followed by reduced-dose and reduced-field irradiation for intracranial GCTs had the same outcome as that reported in the literature, but late adverse effects after treatment were observed. Almost all of the complications were relatively mild but had the potential to lead to psychiatric disorders and intracranial hemorrhaging. ABBREVIATIONS AFP = alpha-fetoprotein; CDC = conventional-dose chemotherapy; CMB = cerebral microbleed; CRT = chemoradiotherapy; CSI = craniospinal irradiation; EP = etoposide and cisplatin; GCT = germ cell tumor; HCG = human chorionic gonadotropin; HDC = high-dose chemotherapy; ICE = ifosfamide, cisplatin, and etoposide; NGGCT = nongerminomatous GCT; OS = overall survival; PBSCT = peripheral blood stem cell transplantation; PFS = progression-free survival; RICM = radiation-induced cavernous malformation; STGC = syncytiotrophoblastic giant cell; SWI = susceptibility-weighted imaging.

Intracranial pressure elevations in diffuse axonal injury: association with nonhemorrhagic MR lesions in central mesencephalic structures

OBJECTIVE

Increased intracranial pressure (ICP) in patients with severe traumatic brain injury (TBI) with diffuse axonal injury (DAI) is not well defined. This study investigated the occurrence of increased ICP and whether clinical factors and lesion localization on MRI were associated with increased ICP in patients with DAI.

METHODS

Fifty-two patients with severe TBI (median age 24 years, range 9-61 years), who had undergone ICP monitoring and had DAI on MRI, as determined using T2*-weighted gradient echo, susceptibility-weighted imaging, and diffusion-weighted imaging (DWI) sequences, were enrolled. The proportion of good monitoring time (GMT) with ICP > 20 mm Hg during the first 120 hours postinjury was calculated and associations with clinical and MRI-related factors were evaluated using linear regression.

RESULTS

All patients had episodes of ICP > 20 mm Hg. The mean proportion of GMT with ICP > 20 mm Hg was 5%, and 27% of the patients (14/52) spent more than 5% of GMT with ICP > 20 mm Hg. The Glasgow Coma Scale motor score at admission (p = 0.04) and lesions on DWI sequences in the substantia nigra and mesencephalic tegmentum (SN-T, p = 0.001) were associated with the proportion of GMT with ICP > 20 mm Hg. In multivariable linear regression, lesions on DWI sequences in SN-T (8% of GMT with ICP > 20 mm Hg, 95% CI 3%-13%, p = 0.004) and young age (-0.2% of GMT with ICP > 20 mm Hg, 95% CI -0.07% to -0.3%, p = 0.002) were associated with increased ICP.

CONCLUSIONS

Increased ICP occurs in approximately one-third of patients with severe TBI who have DAI. Age and lesions on DWI sequences in the central mesencephalon (i.e., SN-T) are associated with elevated ICP. These findings suggest that MR lesion localization may aid prediction of increased ICP in patients with DAI.

Detection of microbleeds associated with sentinel headache using MRI quantitative susceptibility mapping: pilot study

OBJECTSentinel headaches (SHs) associated with cerebral aneurysms (CAs) could be due to microbleeds, which are considered a sign that an aneurysm is unstable. Despite the prognostic importance of these microbleeds, they remain difficult to detect using routine imaging studies. The objective of this pilot study is to detect microbleeds associated with SH using a magnetic resonance imaging (MRI) quantitative susceptibility mapping (QSM) sequence and then evaluate the morphological characteristics of unstable aneurysms with microbleeds.METHODSTwenty CAs in 16 consecutive patients with an initial presentation of headache (HA) leading to a diagnosis of CA were analyzed. Headaches in 4 of the patients (two of whom had 2 aneurysms each) met the typical definition of SH, and the other 12 patients (two of whom also had 2 aneurysms each) all had migraine HA. All patients underwent imaging with the MRI-QSM sequence. Two independent MRI experts who were blinded to the patients' clinical history performed 3D graphical analysis to evaluate for potential microbleeds associated with these CAs. Computational flow and morphometric analyses were also performed to estimate wall shear and morphological variables.RESULTSIn the 4 patients with SH, MRI-QSM results were positive for 4 aneurysms, and hence these aneurysms were considered positive for non-heme ferric iron (microbleeds). The other 16 aneurysms were negative. Among aneurysm shape indices, the undulation index was significantly higher in the QSM-positive group than in the QSM-negative group. In addition, the spatial averaged wall shear magnitude was lower in the aneurysm wall in direct contact with microbleeds.CONCLUSIONSMRI-QSM allows for objective detection of microbleeds associated with SH and therefore identification of unstable CAs. CAs with slightly greater undulation indices are associated with positive MRI-QSM results and hence with microbleeds. Studies with larger populations are needed to confirm these preliminary findings.

Pediatric concussion: biomechanical differences between outcomes of transient and persistent (> 4 weeks) postconcussion symptoms

OBJECTIVE Currently, little is known about the biomechanics of head impact for concussion in youths (ages 5 to 18 years). Even less is known about the biomechanical characteristics and variables related to head impacts that may be useful in differentiating between transient and persistent postconcussion symptoms in a youth population. The purpose of this research was to examine the differences in biomechanics of youth head impact for transient postconcussion symptoms (TPCSs) and persistent postconcussion symptoms (PPCSs) by using data from a hospital population. METHODS In a laboratory setting and using physical, computational, and finite element models, the authors reconstructed falling events in a large cohort of patients who had sustained a brain injury that resulted in transient or persistent postconcussion symptoms. The falling events and resulting concussions for the TPCS and PPCS patient groups were analyzed in terms of force, energy, peak resultant linear and rotational accelerations, and maximum principal strain in the gray and white matter of the brain, as well as measurements of cumulative strain damage. RESULTS The results indicated that there were no significant differences between the groups for any of the variables analyzed. CONCLUSIONS With methods derived for use in an adult population, the magnitudes of peak linear acceleration for the youth data set were determined to be above the 50% risk of injury. The youth data set showed higher brain tissue strain responses for lower energy and impact velocities than measured in adults, suggesting that youths are at higher risk of concussive injury at lower event severities. A trend shown by some variables indicated that larger magnitudes of response were associated with PPCSs, but no single measurement variable consistently differentiated between the TPCS and PPCS groups. It is possible that using the biomechanics of head and brain responses to predict a subjective symptom load may not be appropriate. To enhance future biomechanical analyses, further investigations should include the use of quantifiable measures of brain injury linked to clinical outcomes and possible confounding factors such as history of brain injury and patient predisposition.

Vascular permeability and iron deposition biomarkers in longitudinal follow-up of cerebral cavernous malformations

OBJECTIVE Vascular permeability and iron leakage are central features of cerebral cavernous malformation (CCM) pathogenesis. The authors aimed to correlate prospective clinical behavior of CCM lesions with longitudinal changes in biomarkers of dynamic contrast-enhanced quantitative permeability (DCEQP) and quantitative susceptibility mapping (QSM) assessed by MRI. METHODS Forty-six patients with CCMs underwent 2 or more permeability and/or susceptibility studies in conjunction with baseline and follow-up imaging and clinical surveillance during a mean 12.05 months of follow-up (range 2.4-31.27 months). Based on clinical and imaging features, cases/lesions were classified as stable, unstable, or recovering. Associated and predictive changes in quantitative permeability and susceptibility were investigated. RESULTS Lesional mean permeability and QSM values were not significantly different in stable versus unstable lesions at baseline. Mean lesional permeability in unstable CCMs with lesional bleeding or growth increased significantly (+85.9% change; p = 0.005), while mean permeability in stable and recovering lesions did not significantly change. Mean lesional QSM values significantly increased in unstable lesions (+44.1% change; p = 0.01), decreased slightly with statistical significance in stable lesions (-3.2% change; p = 0.003), and did not significantly change in recovering lesions. Familial cases developing new lesions during the follow-up period showed a higher background brain permeability at baseline (p = 0.001), as well as higher regional permeability (p = 0.003) in the area that would later develop a new lesion as compared with the homologous contralateral brain region. CONCLUSIONS In vivo assessment of vascular permeability and iron deposition on MRI can serve as objective and quantifiable biomarkers of disease activity in CCMs. This may be applied in natural history studies and may help calibrate clinical trials. The 2 techniques are likely applicable in other disorders of vascular integrity and iron leakage such as aging, hemorrhagic microangiopathy, and traumatic brain injury.

Imaging and serum biomarkers reflecting the functional efficacy of extended erythropoietin treatment in rats following infantile traumatic brain injury

OBJECTIVE Traumatic brain injury (TBI) is a leading cause of death and severe morbidity for otherwise healthy full-term infants around the world. Currently, the primary treatment for infant TBI is supportive, as no targeted therapies exist to actively promote recovery. The developing infant brain, in particular, has a unique response to injury and the potential for repair, both of which vary with maturation. Targeted interventions and objective measures of therapeutic efficacy are needed in this special population. The authors hypothesized that MRI and serum biomarkers can be used to quantify outcomes following infantile TBI in a preclinical rat model and that the potential efficacy of the neuro-reparative agent erythropoietin (EPO) in promoting recovery can be tested using these biomarkers as surrogates for functional outcomes. METHODS With institutional approval, a controlled cortical impact (CCI) was delivered to postnatal Day (P)12 rats of both sexes (76 rats). On postinjury Day (PID)1, the 49 CCI rats designated for chronic studies were randomized to EPO (3000 U/kg/dose, CCI-EPO, 24 rats) or vehicle (CCI-veh, 25 rats) administered intraperitoneally on PID1-4, 6, and 8. Acute injury (PID3) was evaluated with an immunoassay of injured cortex and serum, and chronic injury (PID13-28) was evaluated with digitized gait analyses, MRI, and serum immunoassay. The CCI-veh and CCI-EPO rats were compared with shams (49 rats) primarily using 2-way ANOVA with Bonferroni post hoc correction. RESULTS Following CCI, there was 4.8% mortality and 55% of injured rats exhibited convulsions. Of the injured rats designated for chronic analyses, 8.1% developed leptomeningeal cyst-like lesions verified with MRI and were excluded from further study. On PID3, Western blot showed that EPO receptor expression was increased in the injured cortex (p = 0.008). These Western blots also showed elevated ipsilateral cortex calpain degradation products for αII-spectrin (αII-SDPs; p < 0.001), potassium chloride cotransporter 2 (KCC2-DPs; p = 0.037), and glial fibrillary acidic protein (GFAP-DPs; p = 0.002), as well as serum GFAP (serum GFAP-DPs; p = 0.001). In injured rats multiplex electrochemiluminescence analyses on PID3 revealed elevated serum tumor necrosis factor alpha (TNFα p = 0.01) and chemokine (CXC) ligand 1 (CXCL1). Chronically, that is, in PID13-16 CCI-veh rats, as compared with sham rats, gait deficits were demonstrated (p = 0.033) but then were reversed (p = 0.022) with EPO treatment. Diffusion tensor MRI of the ipsilateral and contralateral cortex and white matter in PID16-23 CCI-veh rats showed widespread injury and significant abnormalities of functional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD); MD, AD, and RD improved after EPO treatment. Chronically, P13-P28 CCI-veh rats also had elevated serum CXCL1 levels, which normalized in CCI-EPO rats. CONCLUSIONS Efficient translation of emerging neuro-reparative interventions dictates the use of age-appropriate preclinical models with human clinical trial-compatible biomarkers. In the present study, the authors showed that CCI produced chronic gait deficits in P12 rats that resolved with EPO treatment and that chronic imaging and serum biomarkers correlated with this improvement.

Correlation of the venous angioarchitecture of multiple cerebral cavernous malformations with familial or sporadic disease: a susceptibility-weighted imaging study with 7-Tesla MRI

OBJECTIVE Multiple cerebral cavernous malformations (CCMs) are rare lesions that occur in sporadic or familial form. Depending on the disease form, the natural history and treatment of the lesions strongly vary. Molecular analysis of an underlying germline mutation (CCM1-3) is the most sensitive screening method to distinguish between sporadic and familial cases. However, based on the different pathomechanisms that are believed to be involved in either form, significant distinctions in the CCM-associated cerebral venous angioarchitecture should be detectable. This has not been systematically studied. METHODS A consecutive series of 28 patients with multiple CCMs (681 total) diagnosed on 1.5-T MRI underwent genetic screening for CCM1-3 mutations and high-resolution susceptibility-weighted imaging (SWI) of the cerebral venous angioarchitecture with 7-T MRI. Imaging data were analyzed to examine the CCM-associated venous angioarchitecture. Results were correlated with findings of molecular analysis for CCM1-3 mutations. RESULTS Two different SWI patterns (sporadic and familial) were found. The presence of associated developmental venous anomalies correlated with negative screening for germline mutations (11 sporadic) in all cases. All patients with confirmed familial disease showed normal underlying venous angioarchitecture. Additionally, a very unusual case of a probable somatic mutation is presented. CONCLUSIONS The SWI results of the venous angioarchitecture of multiple CCMs correlate with sporadic or familial disease. These results are consistent with the theory that venous anomalies are causative for the sporadic form of multiple CCMs.

Cerebellar cavernous malformation in pediatric patients: defining clinical, neuroimaging, and therapeutic characteristics

OBJECT

Cerebellar cavernous malformations (CCMs) have not been specifically described in the pediatric age group. Authors of this study, after considering the published literature, describe the characteristic clinical, radiological, and surgical features of CCM in children. METHOSDS: Patients younger than 18 years of age who were known to have CCM and had undergone surgery between 1992 and 2014 at the authors' institution were reviewed. Pediatric CCM cases reported in the literature (case reports and cases included in series on CMs in the pediatric age group) were also analyzed for specific features of this entity.

RESULTS

Four male patients and 1 female patient (2.5-14 years of age) with CCM presented acutely with severe headache followed by cerebellar dysfunction. In all patients, neuroimaging (cranial CT and MRI) demonstrated hemorrhagic cerebellar lesions with heterogeneous T1 and T2 signal intensities and hyperintense blooming on susceptibility-weighted imaging. The lesions reached large sizes exhibiting spherical, cystic, and often "pseudotumoral" morphology. In 3 patients, developmental venous anomalies (DVAs) were found. In 4 of the 5 patients, the CCMs and hematomas were totally removed. All patients had a clinically excellent functional outcome without surgical complication and with complete resolution of their presenting symptoms.

CONCLUSIONS

Cerebellar CMs occur in all pediatric age groups and display characteristic clinical and imaging features. In children, CCMs reach large sizes and can result in massive hemorrhage, often leading to a possible diagnosis of hemorrhage into a tumor. An associated DVA is quite common. Surgery is a safe and efficient treatment option with excellent outcomes in patients.

Neuroimaging findings in pediatric sports-related concussion

OBJECT

The goal in this review was to summarize the results of clinical neuroimaging studies performed in patients with sports-related concussion (SRC) who were referred to a multidisciplinar ypediatric concussion program.

METHODS

The authors conducted a retrospective review of medical records and neuroimaging findings for all patients referred to a multidisciplinary pediatric concussion program between September 2013 and July 2014. Inclusion criteria were as follows: 1) age ≤ 19 years; and 2) physician-diagnosed SRC. All patients underwent evaluation and follow-up by the same neurosurgeon. The 2 outcomes examined in this review were the frequency of neuroimaging studies performed in this population (including CT and MRI) and the findings of those studies. Clinical indications for neuroimaging and the impact of neuroimaging findings on clinical decision making were summarized where available. This investigation was approved by the local institutional ethics review board.

RESULTS

A total of 151 patients (mean age 14 years, 59% female) were included this study. Overall, 36 patients (24%) underwent neuroimaging studies, the results of which were normal in 78% of cases. Sixteen percent of patients underwent CT imaging; results were normal in 79% of cases. Abnormal CT findings included the following: arachnoid cyst (1 patient), skull fracture (2 patients), suspected intracranial hemorrhage (1 patient), and suspected hemorrhage into an arachnoid cyst (1 patient). Eleven percent of patients underwent MRI; results were normal in 75% of cases. Abnormal MRI findings included the following: intraparenchymal hemorrhage and sylvian fissure arachnoid cyst (1 patient); nonhemorrhagic contusion (1 patient); demyelinating disease (1 patient); and posterior fossa arachnoid cyst, cerebellar volume loss, and nonspecific white matter changes (1 patient).

CONCLUSIONS

Results of clinical neuroimaging studies are normal in the majority of pediatric patients with SRC. However, in selected cases neuroimaging can provide information that impacts decision making about return to play and retirement from the sport.

Spreading of multiple Listeria monocytogenes abscesses via central nervous system fiber tracts: case report

Animal studies have shown that Listeria monocytogenes can probably access the brain through a peripheral intraneural route, and it has been suggested that a similar process may occur in humans. However, thus far, its spreading through the central nervous system (CNS) has not been completely elucidated. The authors present a case of multiple L. monocytogenes cerebral abscesses characterized by a pattern of distribution that suggested spread along white matter fiber tracts and reviewed the literature to identify other cases for analysis. They elected to include only those cases with 3 or more cerebral abscesses to make sure that the distribution was not random, but rather followed a pattern. In addition, they included those cases with abscesses in both the brainstem and the cerebral hemispheres, but excluded cases in which abscesses were located solely in the brainstem. Of 77 cases of L. monocytogenes CNS abscesses found in the literature, 17 involved multiple abscesses. Of those, 6 were excluded for lack of imaging and 3 because they involved only the brainstem. Of the 8 remaining cases from the literature, one was a case of bilateral abscesses that did not follow a fiber tract; another was also bilateral, but with lesions appearing to follow fiber tracts on one side; and in the remaining 6, to which the authors added their own case for a total of 7, all the abscesses were located exclusively in the same hemisphere and distributed along white matter fiber tracts. The findings suggest that after entering the CNS, L. monocytogenes travels within the axons, resulting in a characteristic pattern of distribution of multiple abscesses along the white matter fiber tracts in the brain. This report is the first description suggesting intraaxonal CNS spread of L. monocytogenes infection in humans following its entry into the brain. This distinct pattern is clearly seen on imaging and its recognition may be valuable in the diagnosis of listeriosis. This finding may allow for earlier diagnosis, which may improve outcome.

Characterization of radiation-induced cavernous malformations and comparison with a nonradiation cavernous malformation cohort

OBJECT

The objective of this study was to characterize the clinical features of radiation-induced cavernous malformations (RICMs).

METHODS

The authors retrospectively reviewed the clinical and radiological characteristics of patients with RICMs. The features of these RICMs were then compared with features of nonradiation cavernous malformations (CMs) in 270 patients.

RESULTS

Thirty-two patients with RICMs were identified (56.2% men), with a median age of 31.1 years at RICM diagnosis. The median latency from radiation treatment to RICM diagnosis was 12.0 years (interquartile range 5.0-19.6 years). RICMs were always within the previous radiation port. RICMs were symptomatic at diagnosis in 46.9%, and were associated with symptomatic intracranial hemorrhage at any time in 43.8%. Older age at the time of radiation treatment and higher radiation dose were associated with shorter latency. RICMs tended to be diagnosed at a younger age than nonradiation CMs (median 31.1 vs 42.4 years, respectively; p = 0.054) but were significantly less likely to be symptomatic at the time of diagnosis (46.9% vs 65.8%, respectively; p = 0.036). RICMs were more likely to be multiple CMs than nonradiation CMs (p = 0.0002). Prospectively, the risk of symptomatic hemorrhage was 4.2% for RICMs and 2.3% for nonradiation CMs per person-year (p = 0.556). In the absence of symptoms at presentation, the risk of hemorrhage for RICMs was higher than for nonradiation CMs (4.2% vs 0.35%, respectively; p = 0.118).

CONCLUSIONS

In this patient population, RICMs occurred within the radiation port approximately 12 years after radiation treatment. Compared with nonradiation CMs, RICMs were more likely to occur as multiple CMs, to present at a younger age, and were at least as likely to cause symptomatic hemorrhage.