Meningoencephalitis caused by Streptococcus pneumoniae: a diagnostic and therapeutic challenge. Diagnosis with diffusion-weighted MRI leading to treatment with corticosteroids

Localization of cerebral vasculopathy following bacterial meningitis: What can we learn about postinfective ischemic sequelae?

Cerebrovascular complications of bacterial meningitis account for a high incidence of mortality and postinfective neurologic sequelae. Cerebrovascular complications occurring during acute bacterial meningitis are evident from angiographic evidence demonstrating arterial occlusion and vessel wall narrowing, histopathological studies demonstrating vessel wall changes, and radiographic studies demonstrating the presence of brain infarcts. Cerebrovascular disease during bacterial meningitis has been demonstrated in of Haemophilus influenzae, Streptococcus pneumonia, Group B Streptococcus, and Mycobacterium tuberculosis models of meningitis. Despite models of bacterial meningitis showing variable patterns of cerebral vasculopathy as a contributor to different aspects of postinfectious neurological decline, very few studies describe the predominant localization of cerebral vasculopathy with different meningitis causing pathogens. Thus, this review attempts to analyze the different locations of cerebral vasculopathic changes occuring in response to different microbial pathogens and provide a pathophysiologic basis for such an observation.

Meningoencephalitis with Streptococcus equi Subspecies equi Leading to a Dural Arteriovenous Fistula

Invasive infection with Lancefield group C streptococci in humans is extremely rare, with the vast majority of clinical isolates belonging to Streptococcus dysgalactiae subsp. equisimilis. We report a case of meningoencephalitis in a 69-year-old man caused by Streptococcus equi subsp. equi, a microbe that causes strangles in Equus caballus (i.e., the horse). This is only the fourth infection with this subtype of the central nervous system (CNS) reported in humans. The invasiveness of these bacteria, known to be capable of releasing strongly immunogenic exotoxins, is illustrated by white matter lesions that are present in the acute phase. This patient initially recovered well after treatment with antibiotics and glucocorticoids. However, the patient was readmitted 5 months later with multiple intraparenchymatous cerebral haemorrhages. Cerebral angiography confirmed the presence of a suspected superficial dural arteriovenous fistula (DAVF), which is seldom reported after CNS infection. The invasiveness of these bacteria was illustrated by white matter lesions present in the acute phase and the occurrence of a de novo dural arteriovenous fistula in the follow-up period.

Methylprednisolone pulse therapy as an adjuvant treatment of Streptococcus pneumoniae meningitis complicated by cerebral infarction-a case report and review of the literature

PURPOSE

The role of methylprednisolone pulse therapy as adjuvant treatment of Streptococcus pneumoniae meningitis complicated by cerebral infarction has rarely been reported.

METHODS

We reported a case report and also performed a systematic literature review.

RESULTS

A 1-year 2-month-old boy who presented with high fever, status epilepticus, and septic shock was diagnosed with cerebral infarction caused by Streptococcus pneumoniae meningitis on magnetic resonance imaging (MRI). He was treated with methylprednisolone pulse therapy and his clinical condition gradually improved thereafter. At the follow-up visit 1 year after discharge, he was able to sit without support, but he had moderate delays in speech and developmental milestones and epilepsy sequelae.

CONCLUSION

In severe cases, the use of high-dose methylprednisolone should be considered to modulate the inflammatory response in patients with severe cerebral infarction caused by Streptococcus pneumoniae meningitis.

MR imaging of adult acute infectious encephalitis

BACKGROUND

Imaging is a key tool for the diagnosis of acute encephalitis. Brain CT scan must be urgently performed to rule out a brain lesion with mass effect that would contraindicate lumbar puncture. Brain MRI is less accessible than CT scan, but can provide crucial information with patients presenting with acute encephalitis.

METHOD

We performed a literature review on PubMed on April 1, 2015 with the search terms "MRI" and "encephalitis".

RESULTS

We first described the various brain MRI abnormalities associated with each pathogen of acute encephalitis (HSV, VZV, other viral agents targeting immunocompromised patients or travelers; tuberculosis, listeriosis, other less frequent bacterial agents). Then, we identified specific patterns of brain MRI abnomalies that may suggest a particular pathogen. Limbic encephalitis is highly suggestive of HSV; it also occurs less frequently in encephalitis due to HHV6, syphillis, Whipple's disease and HIV primary infection. Rhombencephalitis is suggestive of tuberculosis and listeriosis. Acute ischemic lesions can occur in patients presenting with severe bacterial encephalitis, tuberculosis, VZV encephalitis, syphilis, and fungal infections.

CONCLUSION

Brain MRI plays a crucial role in the diagnosis of acute encephalitis. It detects brain signal changes that reinforce the clinical suspicion of encephalitis, especially when the causative agent is not identified by lumbar puncture; it can suggest a particular pathogen based on the pattern of brain abnormalities and it rules out important differential diagnosis (vascular, tumoral or inflammatory causes).

Streptococcus Pneumoniae Intracranial Abscess and Post-Infectious Vasculitis

Intracranial abscesses are rare complications of Streptococcus pneumoniae infections, and to our knowledge, there have been no case reports of post-infectious vasculitis developing in such patients. Here we describe the case of a 48-year-old post-splenectomy male who developed post-infectious vasculitis following S. pneumoniae otitis media complicated by mastoiditis, osteomyelitis, meningitis, and intracranial abscess. Clinicians ought to be aware of the possible adverse outcomes of invasive S. pneumoniae and the limitations of current treatment options.

Apparent Diffusion Coefficient analysis of encephalitis: A comparative study with topographic evaluation and conventional MRI findings

Objective:

Our purpose was to reveal the efficiency of diffusion weighted imaging (DWI) in the diagnosis of encephalitis, and to determine the relation between the apparent diffusion coefficient (ADC) values, the onset of the clinical symptoms, and the lesion extent.

Methods:

Conventional magnetic resonance imaging (MRI) was performed in 17 patients with encephalitis diagnosed on the basis of laboratory, clinical and radiologic findings during 2009 and 2015. Based on the duration between the onset of the symptoms and the brain MRI findings, the patients were divided into three groups. ADC values of the encephalitis lesion, the lesions’ topographic analysis score, deep gray matter involvement, patients’ clinical situation and the duration of the arrival to the clinic was examined.

Results:

Mean ADC values were 0,988±0,335 x10^-3 mm²/s in group I (0-2 days), 1,045±0,347 x10^-3 mm²/s in Group-II (3-7 days), 1,451±0,225 x10^-3 mm²/s in Group-III (8 days and over). The relation between the ADC values and the duration of the arrival, topographic analysis score, the relation between the patients’ clinical situation and the deep gray matter involvement were found to be statistically significant. The deep gray matter involvement was demonstrated more clearly by FLAIR images when compared with DWI.

Conclusion:

Conventional MRI sequences may be insufficient in showing the encephalitis lesion. DWI must be added to the imaging modalities immediately in the cases suspected of having encephalitis.

Imaging of Cerebral Vasculitis

Background

In young patients, vasculitic stenoses of cerebral blood vessels are an important cause of cerebral ischaemia. Diagnosis may prove very difficult.

Summary of review

The diagnostic process is usually initiated by the detection of brain lesions consistent with cerebral vasculitis. Multiple infarcts of various ages in more than one vascular territory are thought to be suggestive of a vascular inflammatory disease. The next step in the imaging of patients with suspected vasculitis is the search for an underlying vascular stenosis. Today, magnetic resonance angiography is the principal modality for the investigation of patients thought to have intracranial stenoses. At 1·5 T, only large brain arteries can be imaged with a high diagnostic accuracy. Intraarterial DSA remains an indispensable tool for the investigation of medium and small brain artery stenoses.

Conclusions

However, contrast-enhanced magnetic resonance imaging may be able to demonstrate wall thickening and contrast uptake in large cerebral arteries, obviating biopsy in patients with basal vasculitis.

Multiple Brain Abscesses due to Streptococcus anginosus: Prediction of Mortality by an Imaging Severity Index Score

An elderly patient with altered mental status, brain abscesses, ventriculitis, and empyemas died of septic shock and brain abscesses secondary to Streptococcus anginosus despite aggressive treatment. An imaging severity index score with a better prognostic value than the Glasgow coma scale predicted mortality in this patient.

Pneumococcal-meningitis associated acute disseminated encephalomyelitis (ADEM) - case report of effective early immunotherapy

Introduction

Unvaccinated patients with history of splenectomy are prone to fulminant courses of Streptococcus pneumoniae-associated bacterial meningitis. Besides direct brain damage those patients may additionally suffer from parainfectious syndromes, notably vasculitis and acute disseminated encephalomyelitis (ADEM). Differentiation and treatment of these immunological reactions is challenging.

Methods

Case report.

Results

A 61 year-old woman with history of splenectomy without vaccination for S. pneumoniae presented with progressive headache and meningism. CSF-analysis revealed pleocytosis with microbiological evidence for pneumococcal meningitis. After unsuspicious initial cranial CT imaging and initiation of appropriate antibiotic therapy, MRI two days later showed widespread FLAIR- and T2-hyperintense white matter lesions that further progressed upon follow-up MRI and that fulfilled imaging criteria of ADEM. Meanwhile the patient deteriorated and required mechanical ventilation. Cranial angiography showed no signs of vasculitis or vasospasms. Screening for autoimmune diseases remained negative, however oligoclonal bands turned positive. Brain biopsy mainly revealed perivascular CD4+ T-cells and demyelinated areas. Despite ongoing acute meningitis, a 10-day corticosteroid-pulse was initiated followed by steroid-tapering. Within 4 weeks, clinical and MRI findings ameliorated. In an one-year follow-up visit, the patient significantly recovered, MRI lesions were markedly reduced and no further relapses occurred.

Conclusion

Acute pneumococcal meningitis in unvaccinated splenectomized patients may be complicated by a monophasic course of parainfectious ADEM that can be controlled with high-dose corticosteroids. Parainfectious vasculitis or cerebritis are important differential diagnoses and exact differentiation of these entities is important to initiate early appropriate immunotherapy.

Intractable pneumococcal meningoencephalitis associated with a TNF-α antagonist

A 34-year-old man was treated with a TNF-α antagonist for ankylosing spondylitis, and this subsequently developed a CNS infection. Magnetic resonance imaging showed diffuse subcortical white matter lesions. Streptococcus pneumoniae was cultured from the cerebrospinal fluid and blood. The patient died of multifocal widespread brain damage and subarachnoid hemorrhage, despite intensive antibacterial medication. Pneumococcal meningoencephalitis can occur in association with TNF-α antagonists. Clinicians should be aware of both the risk of fatal bacterial meningoencephalitis associated with TNF-α antagonists and the possibility of an unusual presentation of bacterial meningitis.

Concurrent West Nile virus infection in pneumococcal meningitis: clinical and MRI features

We report the clinical and neuroimaging findings of an immunocompetent patient with concurrent pneumococcal and West Nile virus meningoencephalitis with relapsing clinical course despite a full course of antibiotic treatment. The patient developed acute oculomotor nerve palsy with pupillary involvement and bilateral hearing loss, and delayed right leg monoparesis. We speculate that coexisting bacterial and viral neuroinvasive infections contributed to the unusual clinical and imaging manifestations, and that overwhelming laboratory and clinical features of bacterial meningitis masked the typical features of CNS viral infection. Therefore, atypical presentations of bacterial meningitis should raise a high index of suspicion for coexisting infections, even in immunocompetent patients, and evolving neuroimaging findings may be helpful in substantiating clinical suspicion and guiding further management.

Clinical characteristics of streptococcus pneumoniae meningoencephalitis after transsphenoidal surgery: three case reports

We report three extremely rare cases of Streptococcus pneumoniae meningoencephalitis (SPM) after transsphenoidal surgery (TSS). Between 2004 and 2010, we experienced three cases of severe SPM after surgery out of 1,965 patients undergoing TSS (0.15%). The three cases included a 4-year-old boy with a large cystic craniopharyngioma, a 40-year-old man with a non-functioning pituitary adenoma, and a 55-year-old man with acromegaly. The similarity among these SPM patients was that severe clinical events occurred suddenly 1–2 months postoperatively without any history of sinusitis or pneumonia. Despite intensive care these patients notably had residual neurological sequelae. In no case was rhinorrhea associated with SPM. It should be noted that SPM was not detected from bacterial cultures of the sphenoidal sinus mucous membranes (BCSM) obtained during TSS in two of the patients examined. Severe postoperative SPM can occur suddenly without cerebrospinal fluid (CSF) leakage within 2 months after surgery and requires emergency treatment. Reduced resistance to infection may play a role in the occurrence of SPM in our three patients. Our study indicates that BCSM is not useful for predicting postoperative meningitis.

Brucella abortus induces TNF-α-dependent astroglial MMP-9 secretion through mitogen-activated protein kinases

Background

Central nervous system (CNS) invasion by bacteria of the genus Brucella results in an inflammatory disorder called neurobrucellosis. We have recently demonstrated that B. abortus infects microglia and astrocytes, eliciting the production of a variety of pro-inflammatory cytokines which contribute to CNS damage. Matrix metalloproteinases (MMP) have been implicated in inflammatory tissue destruction in a range of pathological situations in the CNS. Increased MMP secretion is induced by pro-inflammatory cytokines in a variety of CNS diseases characterized by tissue-destructive pathology.

Methods

In this study, the molecular mechanisms that regulate MMP secretion from Brucella-infected astrocytes in vitro were investigated. MMP-9 was evaluated in culture supernatants by ELISA, zymography and gelatinolytic activity. Involvement of mitogen-activated protein kinases (MAPK) signaling pathways was evaluated by Western blot and using specific inhibitors. The role of TNF-α was evaluated by ELISA and by assays with neutralizing antibodies.

Results

B. abortus infection induced the secretion of MMP-9 from murine astrocytes in a dose-dependent fashion. The phenomenon was independent of bacterial viability and was recapitulated by L-Omp19, a B. abortus lipoprotein model, but not its LPS. B. abortus and L-Omp19 readily activated p38 and Erk1/2 MAPK, thus enlisting these pathways among the kinase pathways that the bacteria may address as they invade astrocytes. Inhibition of p38 or Erk1/2 significantly diminished MMP-9 secretion, and totally abrogated production of this MMP when both MAPK pathways were inhibited simultaneously. A concomitant abrogation of B. abortus- and L-Omp19-induced TNF-α production was observed when p38 and Erk1/2 pathways were inhibited, indicating that TNF-α could be implicated in MMP-9 secretion. MMP-9 secretion induced by B. abortus or L-Omp19 was completely abrogated when experiments were conducted in the presence of a TNF-α neutralizing antibody. MMP-9 activity was detected in cerebrospinal fluid (CSF) samples from patients suffering from neurobrucellosis.

Conclusions

Our results indicate that the inflammatory response elicited by B. abortus in astrocytes would lead to the production of MMP-9 and that MAPK may play a role in this phenomenon. MAPK inhibition may thus be considered as a strategy to control inflammation and CNS damage in neurobrucellosis.

Brain abscesses complicating acute pneumococcal meningitis during etanercept therapy

Brain abscess formation as a sequelae of community-acquired pneumococcal meningitis is extremely rare, accounting for less than 1% of all meningitis complications. Although metastatic seeding from a distal peripheral septic focus has been observed, this phenomenon most commonly occurs in the context of ear, nose and throat infections, post-cranial neurosurgical procedures, traumatic open cranial injury, or immunosuppression. We present the case of a man, 61 years old, on etanercept therapy for ankylosing spondylitis who developed multiple brain abscesses as a complication of pneumococcal meningitis. We believe that the predisposition to this extremely rare complication of a particularly aggressive pneumococcal meningitis was most likely due to the underlying immunosuppression resulting from etanercept therapy. As far as we know, this case is the first report linking multiple brain abscess formation in a patient with community-acquired pneumococcal meningitis with etanercept therapy.

Paroxysmal autonomic instability with dystonia after pneumococcal meningoencephalitis

Streptococcus pneumoniae is a common cause of bacterial meningitis, frequently resulting in severe neurological impairment. A seven-month-old child presenting with Streptococcus pneumoniae meningoencephalitis developed right basal ganglia and hypothalamic infarctions. Daily episodes of agitation, hypertension, tachycardia, diaphoresis, hyperthermia, and decerebrate posturing were observed. The diagnosis of paroxysmal autonomic instability with dystonia was established. The patient responded to clonidine, baclofen, and benzodiazepines. Although this entity has been reported in association with traumatic brain injury, and as a sequel to some nervous system infections, this is the first case, to our knowledge, associated with pneumococcal meningoencephalitis.

A case of acute encephalopathy with biphasic seizures and late reduced diffusion associated with Streptococcus pneumoniae meningoencephalitis

Acute encephalopathy with biphasic seizures and reduced diffusion (AESD) encompasses a group of encephalopathy characterized by biphasic seizures and disturbance of consciousness in the acute stage followed in the subacute stage by reduced diffusion in the subcortical white matter on magnetic resonance imaging. The etiology of AESD is viral infection and associated pathological changes. Here we report the first case of AESD caused by bacterial infection (Streptococcus pneumoniae meningitis) in a 1-year-old boy.

Streptococcus pneumoniae meningoencephalitis with bilateral basal ganglia necrosis: an unusual complication due to vasculitis

Streptococcus pneumoniae (S pneumoniae) is a common cause of bacterial meningitis, frequently leading to death or severe neurological impairment. We report an exceptional case of a 4-month-old boy with meningitis caused by S pneumoniae. Computed tomography (CT) and magnetic resonance imaging (MRI) examinations of the brain showed bilateral symmetrical necrosis involving the lentiform and caudate nuclei, as well as the thalamus. T1-weighted MR images showed patchy areas of increased signal intensity, consistent with hemorrhagic transformation of the lesions. Autopsy revealed widespread necrosis of the basal ganglia with clear signs of vasculitis. Severe complications of S pneumoniae meningoencephalitis are known in infants but to our knowledge, such lesions in the basal ganglia have only been reported thrice in adults and never in children.

Unusual exanthema combined with cerebral vasculitis in pneumococcal meningitis: a case report

Introduction

Bacterial meningitis is a complex, rapidly progressive disease in which neurological injury is caused in part by the causative organism and in part by the host's own inflammatory responses.

Case presentation

We present the case of a two-year-old Greek girl with pneumococcal meningitis and an atypical curvilinear-like skin eruption, chronologically associated with cerebral vasculitis. A diffusion-weighted MRI scan showed lesions with restricted diffusion, reflecting local areas of immunologically mediated necrotizing vasculitis.

Conclusions

Atypical presentations of bacterial meningitis may occur, and they can be accompanied by serious unexpected complications.

Restricted Diffusion of Pus in the Subarachnoid Space: MRSA Meningo-Vasculitis and Progressive Brainstem Ischemic Strokes - A Case Report

Extra-axial restriction on diffusion weighted imaging (DWI) is an unusual finding on brain magnetic resonance imaging (MRI). Intra-axial restriction on DWI, however, is common, and can represent brain parenchymal infarction, tumor, abscess, or toxic-metabolic process. The infrequency of extra-axial DWI restriction and the paucity of clinico-pathological correlation in the literature limit its differential diagnosis. Scant case reports suggest that extra-axial DWI restriction could be a lymphoma, neurenteric cyst, or, in one patient, subdural empyema [1,2,3]. We postulate that pus formation must be excluded first, because it can provoke an aggressive meningo-vasculitis with rapidly fatal, intra-axial infarctions. Our patient was a 45-year-old man, presenting to our hospital with left facial droop and right (contralateral) arm and leg weakness. Initial MRI revealed DWI restriction in the left lateral pons, consistent with a classic Millard-Gubler stroke. Also noted was a subtle, extra-axial area of curvilinear diffusion restriction in the left cerebellar-pontine angle's subarachnoid space. Days later, the patient had a headache, and repeat MRI revealed extension of the two DWI lesions – both the intra-axial pontine infarction and the extra-axial area of restricted diffusion in the subarachnoid space. The patient became comatose, a third MRI revealed more extensive DWI restrictions, and he expired despite aggressive care. Autopsy revealed massive brainstem infarcts, a thick lymphoplasmacytic infiltrate, copious Gram-Positive cocci (likely MRSA) and arteries partially occluded with fibrointimal proliferation. This emphasizes the concept that extra-axial DWI restriction can represent pus development in the subarachnoid space – a radiographic marker to identify a patient at risk for demise due to septic, meningo-vasculitic infarctions.

Leukoencephalopathy in pneumococcal meningitis: a diagnostic pitfall and treatment challenge

We present a case of pneumococcal meningitis complicated by leukoencephalopathy. Possible pathogenic mechanisms, a diagnostic pitfall, and optimal treatment options are discussed.

Evaluation of cerebral infarction in tuberculous meningitis by diffusion weighted imaging

BACKGROUND

Ischemic complications are known to occur in tuberculous meningitis (TBM). They are usually seen in patients with TBM having a more severe disease. Diffusion weighted imaging (DWI) provides information regarding tissue ischemia at an early stage as compared to conventional magnetic resonance imaging (MRI).

METHODS

Ischemic complications in human immunodeficiency virus (HIV) negative TBM were evaluated using DWI and T2 weighted imaging in 30 patients in the present study. The imaging was performed at baseline within 7 days of admission and in case of any neurological deterioration during follow up. The outcome was assessed by the modified Barthel's index at 1 year follow up. A score of >/=12 was taken as a poor outcome, while a score of <12 was considered as good outcome.

RESULT

Seventeen of these 30 patients had infarcts, and the total number of infarcts seen was 42. Thirty eight lesions were acute/sub acute and four were chronic infarcts. Out of the 38 acute/sub acute infarcts 34 were visible both on T2 weighted imaging and on DWI, while four were seen only on DWI. The volume of infarcts as seen by DWI was significantly larger as compared to conventional T2 weighted imaging (p = 0.019). Six patients had a poor outcome, five from the infarct group and one from the non-infarct group.

CONCLUSION

DWI demonstrates a larger area of infarction and may also be useful in the early detection of infarction. It should be used as an additional sequence along with conventional imaging in patients with TBM while they are on a follow up on anti tuberculous treatment. The information obtained by DWI may be of value in explaining the clinical condition of the patient as well as in the management and prognostication.

[Acute meningoencephalitis caused by Streptococcus pneumoniae, mimicking acute disseminated encephalomyelitis]

A 57-year old woman had a five-day history of cough and high fever followed by abnormal behavior and headache with signs of meningeal irritation. A cerebrospinal fluid (CSF) exam revealed polymorphonuclear pleocytosis. Streptococcus pneumoniae was cultured from the patient's CSF and serum. Clinical features and laboratory investigations supported a diagnosis of pneumococcal meningoencephalitis. After treatment with intravenous meropenem (MEPM), the patient's laboratory data improved and her neck stiffness disappeared, but a brain MRI showed white matter lesions in the bilateral frontal and temporal lobes. The patient responded to pulse therapy with intravenous methylprednisolone (1 g/day), carried out over three days: she recovered neurological function and her MRI lesions resolved. We report a case of acute meningoencephalitis caused by Streptococcus pneumoniae, mimicking acute disseminated encephalomyelitis (ADEM). We suggest that pneumococcal infection is one of the pathogenetic factors in ADEM.

Recurrent Streptococcus Pneumoniae Meningoencephalitis in a Patient With a Transethmoidal eningoencephalocele

We report a case of recurrent Streptococcus Pneumoniae meningoencephalitis with a transethmoidal meningoencephalocele (TEME) but without cerebrospinal fluid (CSF) leakage.

A 35-year-old man was admitted with S. pneumoniae meningitis. He had suffered from four episodes of recurrent pneumococcal meningitis during the previous 4 years. A computed tomography scan of the paranasal sinus showed the TEME protruding through a bony defect of the right frontal base. However, the patient did not have symptoms that could be attributable to CSF leakage, and radioisotope cisternography did not identify a leak. Brain magnetic resonance imaging revealed cortical lesions overlying the TEME, and electroencephalography revealed epileptiform discharges in frontal regions. Appropriate antibiotics therapy without steroids was given to improve his condition.

The presented case suggests that even in the absence of clinically demonstrable CSF leakage, an occult skullbase defect and its associated meningoencephalocele should be considered in patients with recurrent bacterial meningitis.

Streptococcus pneumoniae meningoencephalitis with unusual and widespread white matter lesions

Streptococcus pneumoniae is a common cause of bacterial meningitis, frequently leading to death or severe neurological impairment. We report an exceptional case of a 7-month-old child with meningoencephalitis caused by S. pneumoniae. Peculiar, widespread and unique signal abnormalities were found on magnetic resonance imaging (MRI) with extensive central nervous white matter injury as well as evidence of thrombosis of the lateral transverse sinus. These changes were observed very early in the course of the illness, presumably reflecting widespread cytotoxic edema, vasculitis and acute demyelination. These lesions occurred despite appropriate antibiotic and anti-inflammatory (glucocorticoid) therapy started very early in the course of the disease. Such diffuse white matter lesions in the early course of (pediatric) cases of S. pneumoniae meningoencephalitis have not been reported previously.

Cerebral vasculitis: imaging signs revisited

Inflammatory stenoses of cerebral blood vessels, although rare in general, are an important cause of cerebral ischemia in younger patients. The diagnosis is often difficult. The first step in the diagnostic process is the identification of brain lesions consistent with cerebral vasculitis. Brain lesions are frequently found in this patient group, especially if modern imaging tools such as diffusion and perfusion-weighted imaging are employed. Although no specific pattern for this entity exists, multiple infarcts of various ages in more than one vascular territory should raise this suspicion. The next step in the imaging of patients with suspected vasculitis is the demonstration of the underlying vascular pathology. MR angiography is the mainstay of investigating patients for intracranial vascular stenoses. However, at 1.5 T it is only diagnostic for stenoses of large brain arteries. Hence, conventional angiography is still required to investigate stenoses of medium and small-sized brain arteries. Recent work suggests that MRI can directly demonstrate mural thickening and contrast enhancement in basal brain arteries, rendering biopsy obsolete in this patient group. A classification for cerebral vasculitis is proposed according to the size of the affected brain vessels, analogous to the pertinent nomenclature of primary systemic vasculitis.

Streptococcus equi meningoencephalomyelitis in a foal

CASE DESCRIPTION

A 4-month-old American Paint Horse colt was evaluated because of acute onset of ataxia, left-sided head tilt, and fever and a recently noticed heart murmur. Upper respiratory tract infection caused by Streptococcus equi subsp equi had been diagnosed at 3 months of age.

CLINICAL FINDINGS

Hematologic abnormalities included leukocytosis, mature neutrophilia, monocytosis, and mild anemia. Analysis of a CSF sample revealed high total protein concentration and total nucleated cell count; nucleated cells consisted mainly of degenerate neutrophils. Results of a real-time PCR assay were positive for S equi subsp equi, and a diagnosis of S equi subsp equi meningoencephalomyelitis was made.

TREATMENT AND OUTCOME

Treatment included administration of potassium penicillin and fluids, but the foal developed uroperitoneum and was subsequently euthanized. Postmortem examination revealed meningoencephalomyelitis, and S equi subsp equi was cultured from a brain aspirate. Additional findings included suppurative cystitis with rupture and neutrophilic myocarditis.

CLINICAL RELEVANCE

Findings suggest that S equi subsp equi meningoencephalomyelitis should be considered in the differential diagnosis for foals with neurologic signs that have a history of strangles or exposure to affected horses.

Diffusion-weighted MR imaging of viral encephalitis

INTRODUCTION

The aim of this study was to evaluate the role of diffusion-weighted imaging (DWI) in the diagnosis of viral encephalitis and its relationship with the stage of the illness.

METHODS

We performed conventional magnetic resonance imaging (MRI) including T1-W, T2-W and fluid attenuated inversion recovery (FLAIR) sequences and DWI in 18 patients with viral encephalitis diagnosed on the basis of laboratory, clinical and radiologic findings. Based on the qualitative and quantitative comparison of the conventional MRI and DWI, the patients were divided into three groups. Apparent diffusion coefficient (ADC) values of the involved and contralateral normal brain tissues were computed and compared for each group. The degree of correlation between the time (TI) from the onset of neurologic symptoms to the MR examination and ADC values was determined.

RESULTS

In group I (n=11) DWI was superior to conventional MRI in detecting the encephalitic involved sites and in depicting the borders of the encephalitic lesions. In group II (n=4) DWI was similar to conventional MRI. In group III (n=3) conventional MRI was superior to DWI. Mean ADC values of affected versus contralateral normal brain tissues were 0.458+/-0.161 x 10(-3) versus 0.86+/-0.08 x 10(-3) in group I, 0.670+/-0.142 x 10(-3) versus 0.93+/-0.07 x 10(-3) in group II, and 1.413+/-0.211 x 10(-3) versus 1.05+/-0.06 x 10(-3) in group III. Patients in group I had significantly lower ADC values than those in group II, while patients in group III had the highest ADC values (P<0.05). The ADC values were significantly lower in the affected sites than in the unaffected sites of patients in groups I and II, but were significantly higher in the affected sites than in the unaffected sites of patients in group III (P<0.05). There was an excellent correlation between ADC values and duration of the disease (r=0.874, P=0.01).

CONCLUSION

DWI is superior to other conventional diagnostic MR sequences in the detection of early viral encephalitic lesions and depiction of the lesion borders and, in combination with other sequences, DWI may contribute to the determination of the disease phase.