Cerebral mucormycosis: proton MR spectroscopy and MR imaging

Rhino-orbito-cerebral Mucormycosis: Pictorial Review

Mucormycosis (MCR) is a fulminant, potentially lethal, opportunistic fungal infection. Diabetes, immunocompromised states and elevated serum iron levels are the most important risk factors for contracting MCR infection. Recently, MCR co-infections have been observed in patients with COVID-19 disease owing to a complex interplay of metabolic factors and corticosteroid therapy. Rhino-orbito-cerebral mucormycosis (ROCM) is the most common clinical form of MCR infection and refers to infection of the nasal cavities, paranasal sinuses, neck spaces, orbits and intracranial structures. Sinonasal inoculation is typically the primary site of infection; the necrotising and angioinvasive properties of the fungus facilitate its spread into adjacent structures. In this review, we discuss the pertinent mycology and risk factors of MCR infection. The review also aims to acquaint the reader with the cross-sectional imaging appearances of ROCM and its complications. All the cases discussed in this pictorial essay are microbiologically and/or histopathologically proven cases of ROCM with concomitant COVID-19 infection.

Rhino-orbital-cerebral mucormycosis in times of COVID-19: A neurosurgical experience

Background:

The gravity of “second wave” of COVID-19 has effaced many new challenges in India; mucormycosis being a recent one. Diabetes mellitus (DM) is a known significant risk factor for mucormycosis. Here, we present our experience with rhino-orbital-cerebral mucormycosis (ROCM) during the “second wave of COVID-19” at a tertiary health care centre in North India.

Methods:

This case series includes four cases of ROCM that were managed by our neurosurgical team in view ofcerebral involvement.

Results:

All the cases with an exception of one (Case 1), had a history of treatment for COVID-19 pneumonia. Case 2, 3 had undergone functional endoscopic sinus surgery (FESS) and orbital decompression before the onset of cerebral involvement; Case 4 underwent FESS and cranial surgery in the same sitting. All the patients had a history of DM and all the cases treated for COVID-19 pneumonia had a history of treatment with corticosteroids. Two patients underwent surgery with the exception of one patient, who did not provide consent for the same. One patient expired before surgical excision could be attempted.

Conclusion:

Regular and intensive follow-up is the key in swift detection and management of ROCM in post-COVID patients. While surgical excision is advisable in the fungal lesion, it must be borne in mind that radical excision of cerebral lesions is associated with morbidity, delayed recovery, and prolonged ICU stay. Culture and sensitivity-based antibiotics should be used judiciously as fever is a common postoperative complication. Blood sugar monitoring and control of DM are paramount in this condition. Steroids should be avoided in the management of cerebral edema with judicious use of hypertonic saline or mannitol.

Utility of 3T single-voxel proton MR spectroscopy for differentiating intracranial meningiomas from intracranial enhanced mass lesions

Background

Proton magnetic resonance spectroscopy (MRS) provides structural and metabolic information that is useful for the diagnosis of meningiomas with atypical radiological appearance. However, the metabolite that should be prioritized for the diagnosis of meningiomas has not been established.

Purpose

To evaluate the differences between the metabolic peaks of meningiomas and other intracranial enhanced mass lesions (non-meningiomas) using MR spectroscopy in short echo time (TE) spectra and the most useful metabolic peak for discriminating between the groups.

Material and Methods

The study involved 9 meningiomas, 22 non-meningiomas, intracranial enhancing tumors and abscesses, and 15 normal controls. The ranking of the peak at 3.8 ppm, peak at 3.8 ppm/Creatine (Cr), β-γ Glutamine-Glutamate (bgGlx)/Cr, N-acetyl compounds (NACs)/Cr, choline (Cho)/Cr, lipid and/or lactate (Lip-Lac) at 1.3 ppm/Cr, and the presence of alanine (Ala) were derived. The metabolic peaks were compared using the Mann-Whitney U test. ROC analysis was used to determine the cut-off values for differentiating meningiomas from non-meningiomas using statistically significant metabolic peaks.

Results

The ranking of the peak at 3.8 ppm among all the peaks, peak at 3.8 ppm/Cr, bgGlx/Cr, Lip-Lac/Cr, and the presence of Ala discriminated meningiomas from non-meningiomas with moderate to high accuracy. The highest accuracy was 96.9% at a threshold value of 3 for the rank of the peak at 3.8 ppm.

Conclusion

A distinct elevated peak at 3.8 ppm, ranked among the top three highest peaks, allowed the detection of meningiomas.

Mucormycosis of the Central Nervous System

Mucormycosis involves the central nervous system by direct extension from infected paranasal sinuses or hematogenous dissemination from the lungs. Incidence rates of this rare disease seem to be rising, with a shift from the rhino-orbital-cerebral syndrome typical of patients with diabetes mellitus and ketoacidosis, to disseminated disease in patients with hematological malignancies. We present our current understanding of the pathobiology, clinical features, and diagnostic and treatment strategies of cerebral mucormycosis. Despite advances in imaging and the availability of novel drugs, cerebral mucormycosis continues to be associated with high rates of death and disability. Emerging molecular diagnostics, advances in experimental systems and the establishment of large patient registries are key components of ongoing efforts to provide a timely diagnosis and effective treatment to patients with cerebral mucormycosis.

Diagnosis and Treatment of Isolated Cerebral Mucormycosis: Patient-Level Data Meta-Analysis and Mayo Clinic Experience

BACKGROUND

Isolated cerebral mucormycosis is a rare and serious infection associated with intravenous drug abuse.

METHODS

We performed a comprehensive meta-analysis of cases reported in studies and have included an unreported case from our institution. We searched PubMed/Medline, EMBASE, Scopus, Cochrane Databases, and our institution's electronic medical health records from inception through March 31, 2018. The cases were considered isolated (only affecting the cerebrum, cerebellum, or brainstem) if the absence of other primary sources of infection had been documented. Continuous variables were summarized using the median and interquartile range and categorical variables using frequencies and proportions. The relationships between variables were tested using the Wilcoxon rank sum and Pearson χ² tests.

RESULTS

A total of 130 studies (141 patients) met the eligibility requirements and were screened; 68 patients were included. The median age was 28 years (interquartile range, 24-38); 57% were men. Most patients had a history of intravenous drug abuse (82%), and 20% had positive human immunodeficiency virus findings. The lesion location was mostly supratentorial (91%), especially in the basal ganglia (71.2%). The cultures were positive in 38%, with Rhizopus the most common organism (59%). The mortality rate was 65%. The survivors were significantly more likely to have received amphotericin B (92% vs. 43%; P < 0.001) or to have undergone stereotactic aspiration (58% vs. 25%; P < 0.01).

CONCLUSIONS

Isolated cerebral mucormycosis has a pooled mortality rate of 65%. The presence of lesions in the basal ganglia, rapidly progressive symptoms, and a history of intravenous drug abuse should raise suspicion for the early initiation of amphotericin B and stereotactic aspiration.

Multimodality imaging in cranial blastomycosis, a great mimicker: Case-based illustration with review of clinical and imaging findings

We describe the clinical, laboratory, and imaging data of three patients who are proven cases of blastomycosis with cranial involvement. In this review, we discuss the imaging features of cranial blastomycosis with relevant clinical case examples including computed tomography (CT), magnetic resonance imaging (MRI), and advanced MR imaging techniques like magnetic resonance spectroscopy (MRS) and MR perfusion. Literature is reviewed for modern-day diagnosis and treatment of this fatal intracranial infection, if not diagnosed promptly and managed effectively.

MR spectroscopy of intracranial tuberculomas: A singlet peak at 3.8 ppm as potential marker to differentiate them from malignant tumors

PURPOSE

The diagnosis of intracranial tuberculomas is often challenging. Our purpose is to describe the most common metabolic patterns of tuberculomas by MR spectroscopy (MRS) with emphasis on potential specific markers.

METHODS

Single-voxel MRS short echo time was performed in 13 cases of tuberculomas proven by histology and/or response to anti-mycobacterial therapy. For comparison MRS was also performed in 19 biopsy-proven malignant tumors (13 high-grade gliomas and six metastasis). Presence of metabolic peaks was assessed visually and categorical variables between groups were compared using chi-square. Metabolite ratios were compared using Mann-Whitney test and diagnostic accuracy of the metabolite ratios was compared using receiver-operating characteristic (ROC) curves analysis.

RESULTS

Spectroscopic peaks representing lipids and glutamate/glutamine (Glx) as well as a peak at ∼3.8 ppm were well defined in 77% (10/13), 77% (10/13) and 69% (nine of 13) of tuberculomas, respectively. Lipid and Glx peaks were also present in most of the malignant lesions, 79% (15/19) and 74% (14/19) respectively. However, a peak at ∼3.8 ppm was present in only 10% (two of 19) of the tumor cases (p < 0.001). Higher Cho/Cr and mI/Cr ratios helped discriminate malignant lesions with an area under the ROC curve of 0.86 (SE: 0.078, p < 0.002, CI: 0.7-1) and 0.8 (SE: 0.1, p < 0.009, CI: 0.6-1), respectively. Threshold values between 1.7-1.9 for Cho/Cr and 0.8-0.9 for mI/Cr provided high specificity (91% for both metabolites) and adequate sensitivity (75% and 80%, respectively) for discrimination of malignant lesions.

CONCLUSION

A singlet peak at ∼3.8 ppm is present in the majority of tuberculomas and absent in most malignant tumors, potentially a marker to differentiate these lesions. The assignment of the peak is difficult from our analysis; however, guanidinoacetate (Gua) is a possibility. Higher Cho/Cr and mI/Cr ratios should favor malignant lesions over tuberculomas. The presence of lipids and Glx is non-specific.

Infektionen

In diesem Kapitel werden zunächst die für die Neurointensivmedizin wesentlichen bakteriellen Infektionen (Meningitis, spinale und Hirnabszesse, Spondylodiszitis, septisch-embolische Herdenzephalitis) abgehandelt, die trotz gezielt eingesetzter Antibiotika und neurochirurgischer Therapieoptionen noch mit einer erheblichen Morbidität und Mortalität behaftet sind. Besonderheiten wie neurovaskuläre Komplikationen, die Tuberkulose des Nervensystems, Neuroborreliose, Neurosyphilis und opportunistische Infektionen bei Immunsuppressionszuständen finden hierbei besondere Berücksichtigung. Der zweite Teil dieses Kapitels behandelt akute und chronische Virusinfektionen des ZNS sowie in einem gesonderten Abschnitt die HIVInfektion und HIV-assoziierte Krankheitsbilder sowie Parasitosen und Pilzinfektionen, die in Industrieländern seit Einführung der HAART bei HIV zwar eher seltener, aber mit zunehmender Globalisierung auch in unseren Breiten immer noch anzutreffen sind.

Magnetic resonance spectroscopy imaging characteristics of cerebral Blastomycosis

BACKGROUND

Blastomycosis is a dimorphic fungus that is endemic to the midwest and southwestern United States. Involvement of the central nervous system (CNS) is thought to only represent 5-10% of cases of disseminated Blastomycosis.

CASE DESCRIPTION

A 54-year-old Caucasian female presented to the Neurosurgery service with a 1-day history of progressive right sided hemiparesis. Magnetic resonance imaging (MRI) demonstrated a 2 × 4 cm heterogeneous intracranial mass lesion involving the left motor cortex and extending into the ipsilateral parietal lobe. Single-voxel magnetic resonance spectroscopy (MRS) over the enhancing area demonstrated diminished N-acetyl aspartate (NAA) to creatine ratio (1.10), normal choline to NAA ratio (0.82), normal choline to creatine ratio (0.9), and a diminished myoinositol to creatine ratio (0.39). There appeared to be peaks between 3.6 and 3.8 ppm over the enhancing area that were not present in the contralateral normal brain and thought to represent a "trehalose" peak. Due to worsening symptoms and uncertain preoperative diagnosis, the patient underwent a left fronto-parietal craniotomy for open surgical biopsy with possible resection approximately one month after presentation. Pathological analysis confirmed the diagnosis of Blastomycosis.

CONCLUSION

We present the second documented case of intracranial Blastomycosis with MRS imaging. There appears to be a characteristic peak between 3.6 and 3.8 ppm that is thought to represent a "trehalose" peak. This peak is rather specific to fungi and can be helpful in differentiating fungal abscesses from pyogenic abscesses and malignant neoplasms.

MR spectroscopy in brain infections

Infection of the central nervous system can be life-threatening and hence requires early diagnostic support for its optimal management. Routine definitive laboratory diagnostic tests can be time-consuming and delay definitive therapy. Noninvasive imaging modalities have established themselves in the diagnosis of various neurologic diseases. In this article, a pragmatic review of the current role of magnetic resonance spectroscopy in the diagnosis and management of intracranial infections is addressed.

Infektionen

Trotz Weiterentwicklung moderner Antibiotika in den letzten Jahren sind die Letalitätszahlen der bakteriellen (eitrigen) Meningitis weiterhin hoch; Überlebende haben häufig neurologische Residuen. Die ungünstigen klinischen Verläufe der bakteriellen Meningitis sind meist Folge intrakranieller Komplikationen, wie z. B. eines generalisierten Hirnödems, einer zerebrovaskulären arteriellen oder venösen Beteiligung oder eines Hydrozephalus.

Utility of in vitro proton magnetic resonance spectroscopy in aetiological characterisation of brain abscesses

PURPOSE

Brain abscesses often present an aetiological dilemma. Microscopy is insensitive and culture techniques are time consuming. Hence, a new rapid technique in vitro Proton Magnetic Resonance Spectroscopy (1HMRS) was evaluated for its usefulness in the identification of aetiology of brain abscesses.

MATERIALS AND METHODS

A total of 39 pus specimens from brain abscesses were subjected to in vitro 1HMRS. These pus specimens were also processed by conventional culture methods. The spectral patterns generated by in vitro 1HMRS were further correlated with culture results.

RESULTS

Pus specimens which showed the presence of anaerobes on culture revealed the presence of multiplet at 0.9 ppm (100%), lactate-lipid at 1.3 ppm (100%), acetate at 1.92 ppm (100%) and succinate at 2.4 ppm (75%). Pus specimens that revealed the presence of facultative anaerobes on culture showed a pattern B, i.e., the presence of lactate-lipid at 1.3 ppm (100%), acetate at 1.92 ppm (88.88%) along with the multiplet at 0.9 ppm (100%). Pattern C was seen in aerobic infection which showed the presence of lactate-lipid at 1.3 ppm (100%) along with the multiplet at 0.9 ppm. Pus from two tuberculous abscesses showed the complete absence of multiplet at 0.9 ppm.

CONCLUSIONS

We observed in this study that it was possible to differentiate bacterial and tuberculous brain abscesses using in vitro 1HMRS. Further, it was also possible to distinguish between aerobic and anaerobic brain abscesses on the basis of spectral patterns. In vitro 1HMRS of fungal and actinomycotic brain abscess are also presented for its unusual spectra.

Successful treatment of a giant isolated cerebral mucormycotic (zygomycotic) abscess using endoscopic debridement: case report and therapeutic considerations

BACKGROUND

Cerebral mucormycosis without rhino-orbital or systemic involvement is an extremely rare condition mostly associated with parenteral drug abuse.

CASE DESCRIPTION

We report the case of a 42-year-old woman who presented with hemiparesis of the left side and altered mental status. Neuroradiologic workup demonstrated an inflammatory lesion involving the right basal ganglia. Proton magnetic resonance spectroscopy demonstrated features consistent with a pyogenic abscess. Computed tomography-guided stereotactic biopsy led to the diagnosis of cerebral mucormycosis. Parenteral AMB-L treatment was conducted, but the patient worsened clinically, presenting with a complete hemiplegia, and cerebral magnetic resonance imaging (MRI) scans demonstrated a voluminous abscess formation. Then, under stereotactic guidance, a surgical endoscopic debridement of the abscess cavity associated with the placement of an Ommaya reservoir was performed. Systemic and intralesional treatment with AmB associated with an adjunctive immune therapy was conducted. At 3-year follow-up, the patient had recovered partially from her left hemiplegia, allowing her to walk without help, and cerebral MRI scans showed complete resorption of the abscess.

CONCLUSION

Our good results suggest that surgical endoscopic debridement associated with intravenous and intracavitary antifungal therapy might be valuable in treating voluminous deep-seated mucormycotic lesions.

Rhino-orbital-cerebral mucormycosis with different cerebral involvements: infarct, hemorrhage, and ophthalmoplegia

Rhino-orbital-cerebral mucormycosis is a rare but often fatal opportunistic necrotizing infection of the sinuses, orbit, and brain caused by saprophytic fungi. It usually develops in patients with diabetes or immune system deficiency. In this study, imaging features in 3 patients with rhino-orbital-cerebral mucormycosis who presented with various symptoms and different cerebral involvements are discussed. Headache, blurred vision, fever, painful ophthalmoplegia, and cranial nerve involvement were among the clinical findings. Computed tomography and magnetic resonance imaging are the best imaging methods for assessing the extent of this disease. Relatively typical but nonspecific characteristics are bone destruction, vascular invasion, and central hypointensity in the paranasal sinuses or an intracranial mass that is revealed by T(2)-weighted magnetic resonance imaging. Imaging findings include cavernous sinus involvement, cerebral infarct, and intracerebral hemorrhage. Because of the invasive and fulminant nature of rhino-orbital-cerebral mucormycosis, successful treatment seems to be based on early diagnosis and on the management of underlying immunologic problems.

Magnetic resonance spectroscopy in the diagnosis and etiological definition of brain bacterial abscesses

We report two patients with bacterial brain abscesses whose etiological diagnosis was correctly proposed by association of diffusion weighted images (DWI) and magnetic resonance spectroscopy (MRS) with conventional MRI. Both patients presented ring enhancing lesions with evidences of restricted diffusion. On MRS, the abscess caused by aerobic bacteria presented lactate and aminoacids peaks and the abscess caused by anaerobic facultative bacteria showed also acetate and succinate peaks. These results are in agreement with an unique previous study that related MRS pattern with bacterial etiology. Conventional MRI, associated with DWI and MRS is effective in diagnosing bacterial abscess and promising in exploring its etiology.

Comparative evaluation of fungal, tubercular, and pyogenic brain abscesses with conventional and diffusion MR imaging and proton MR spectroscopy

BACKGROUND AND PURPOSE

It is difficult to differentiate the cause of brain abscesses with the use of CT and MR imaging. We did a comparative evaluation of pyogenic, tubercular, and fungal brain abscesses by using conventional, diffusion-weighted imaging (DWI), and proton MR spectroscopy (PMRS) with an aim to define the unique features that may differentiate among the pyogenic, tubercular, and fungal brain abscesses.

MATERIALS AND METHODS

We performed a retrospective analysis on 110 patients with surgically proved brain abscesses. Imaging studies included T2, T1, postcontrast T1, DWI, and PMRS. Apparent diffusion coefficient (ADC) of the wall and cavity of the abscesses were quantified. The morphologic, physiologic, and metabolite features of pyogenic (n=91), tubercular (n=11), and fungal (n=8) abscesses were compared.

RESULTS

The pyogenic abscesses had smooth (55/91) and lobulated (36/91) walls, whereas the tubercular abscesses had smooth (4/11), lobulated (6/11), or crenated walls (1/11) with no intracavitary projections. The fungal abscesses showed irregular walls (lobulated 4/8, crenated 4/8) with intracavitary projections (8/8). The wall as well as the cavity showed low ADC in the pyogenic and tubercular abscesses. In the fungal abscesses, the wall and projections showed low ADC (8/8); however, the cavity itself showed high ADC (8/8). PMRS showed cytosolic amino acids (89/91), acetate (25/91), and succinate (18/91) in the pyogenic abscesses, whereas lipid/lactate (11/11) was seen in the tubercular abscesses. The fungal abscesses showed lipid (4/8), lactate (7/8), amino acids (4/8), and multiple peaks between 3.6 and 3.8 ppm assigned to trehalose (5/8).

CONCLUSION

Based on the morphologic, ADC, and metabolite information, it may be possible to differentiate among the pyogenic, tubercular, and fungal brain abscesses.

Imaging of isolated cerebral mucormycosis. A report of three cases

Mucormycosis is a rare infection in immunosupressed patients caused by fungi from the family Mucoraceae. Three types of disease spread have been described: rhinocerebral, systemic and isolated. Isolated spread is the most uncommon form, usually resulting in death. It has been described in diabetics, immunosupressed patients and intravenous drug abusers. Neuroimaging can aid the diagnosis of this entity, but biopsy remains the only reliable method. Imaging findings of Mucormycosis include abscesses and hemorrhagic or ischemic infarcts, usually in the basal ganglia and frontal lobes. Single or multiple lesions have been described as well as meningoencephalitis. Understanding these findings can help to detect the infection in an early stage. We describe three cases of isolated cerebral mucormycosis; all of them were intravenous drug abusers with one patient also being HIV positive.

Disseminated mucormycosis in haematological patients: CT and MRI findings with pathological correlation

Disseminated mucormycosis is a rare, mostly fatal infectious complication in immunocompromised haematological patients. The purpose of our study was to describe the multiorgan manifestations of disseminated mucormycosis documented at CT and MRI in four patients and correlate these with the pathological findings and patient outcome. Irrespective of the site of infection, infarction or haemorrhage are the constant features of invasive mycosis. Identification of one or both of these two major imaging findings in immunocompromised patients should be regarded as an indicator of possible infection by angiotropic fungi, including the genre Mucorales.

Identification of diffuse and focal brain lesions by clinical magnetic resonance spectroscopy

The purpose of this paper is to facilitate the comparison of magnetic resonance (MR) spectra acquired from unknown brain lesions with published spectra in order to help identify unknown lesions in clinical settings. The paper includes lists of references for published MR spectra of various brain diseases, including pyogenic abscesses, encephalitis (herpes simplex, Rasmussen's and subacute sclerosing panencephalitis), neurocysticercosis, tuberculoma, cysts (arachnoid, epidermoid and hydatid), acute disseminated encephalomyelitis (ADEM), adrenoleukodystrophy (ALD), Alexander disease, Canavan's disease, Krabbe disease (globoid cell leukodystrophy), Leigh's disease, megalencephalic leukoencephalopathy with cysts, metachromatic leukodystrophy (MLD), Pelizaeus-Merzbacher disease, Zellweger syndrome, HIV-associated lesions [cryptococcus, lymphoma, toxoplasmosis and progressive multifocal leukoencephalopathy (PML)], hydrocephalus and tuberous sclerosis. Each list includes information on the echo time(s) (TE) of the published spectra, whether a control spectrum is shown, whether the corresponding image and voxel position are shown and the patient ages if known. The references are listed in the approximate order of usefulness, based on spectral quality, number of spectra, range of echo times and whether the voxel positions are shown. Spectra of Zellweger syndrome, cryptococcal infection, toxoplasmosis and lymphoma are included, along with a spectrum showing propanediol (propylene glycol).

Succinate in dystrophic white matter: a proton magnetic resonance spectroscopy finding characteristic for complex II deficiency

A deficiency of succinate dehydrogenase is a rare cause of mitochondrial encephalomyopathy. Three patients, 2 sisters and 1 boy from an unrelated family, presented with symptoms and magnetic resonance imaging signs of leukoencephalopathy. Localized proton magnetic resonance spectroscopy indicated a prominent singlet at 2.40ppm in cerebral and cerebellar white matter not present in gray matter or basal ganglia. The signal was also elevated in cerebrospinal fluid and could be identified as originating from the two equivalent methylene groups of succinate. Subsequently, an isolated deficiency of complex II (succinate:ubiquinone oxidoreductase) was demonstrated in 2 patients in muscle and fibroblasts. One of the sisters died at the age of 18 months. Postmortem examination showed the neuropathological characteristics of Leigh syndrome. Her younger sister, now 12 months old, is also severely affected; the boy, now 6 years old, follows a milder, fluctuating clinical course. Magnetic resonance spectroscopy provides a characteristic pattern in succinate dehydrogenase deficiency.