Neuro ID Flashcards
Meningitis
Purulent material in the subarachnoid space from abundant PMNs
Abscess(bottom)
– Occur at the gray-white junction often with marked edema out of proportion to the size of the abscess.
– Necrotic core surrounded by a thick wall of fibroblasts (circle) and proliferating blood vessels
Granulomas
Composed of epitheliod macrophages (closed arrow), multinucleate giant cells (circle), lymphocytes (open arrow)
Caused by:
– Tuberculosis
– Fungi
– Spirochetes
– Sarcoidosis(non-caseating)
– Foreignbody
TB meningitis
Subacute to chronic course
Tuberculosis, fungus, and spirochetes have a predilection for the base of the brain.
Tuberculosis and other mycobacterium are acid- fast bacteria (arrow).
Fungi as hyphae
Aspergillus
– Presents most commonly as infarction (since it is angioinvasive) and less frequently as an abscess usually in immuno- compromised patients
– Narrow regular hyphae branching at acute angles (arrow) invading blood vessels.
A for acute
This patient has aspergillosis, which is caused by the aspergillus fungus. This organism is capable of causing various manifestations, such as allergic syndromes, respiratory tract infections, and sinusitis. However, it may also cause an invasive syndrome that can spread to the CNS, especially in neutropenic patients, immunocompromised patients, or those chronically on steroids.Aspergillus fumigatus is the organism that causes most of the invasive syndromes, invading blood vessels, causing stroke-like syndromes, infarcts, and hemorrhagic transformation. A vasculitis- type phenomenon occurs as the fungus invades the vessel walls and may eventually progress to parenchymal disease, forming granulomas, and abscesses. This fungus may invade multiple other organs and cause systemic disease.
Histopathologically, invading hyphae are detected in blood vessels, with the findings of necrosis, hemorrhage, and inflammation. The specimen shown in Figure 15.8 is a Gomori methenamine silver stain demonstrating septate hyphae that branch at acute angles, which is consistent with aspergillus infection. Aspergillosis does not typically present with meningitis.
Cryptococcus causes meningitis and not typically a vasculitis-type syndrome. Histoplasmosis causes pulmonary disease more frequently, but when it invades the CNS, it can produce a form of basilar meningitis, focal cerebritis, or granulomas. Candidiasis can also cause systemic disease, with histopathological findings of budding yeasts and pseudohyphae. This patient does not have clinical features or pathologic findings of HSV encephalitis (discussed in question 37).
Fungi as hyphae
Mucormycosis (bottom)
– Presents with rhinocerebral disease typically in diabetics, transplant patients, hematologic malignancies
– Triad of DKA, blackened nares, and ophthalmoplegia
– Can also cause infarcts since it is angioinvasive.
– Broad irregular hyphae branching at 90 degrees (circle).
– High mortality: 44%
A zygomycosis.
This fungus tends to enter through the respiratory tract, producing nasal and sinus disease and pulmonary infections. In the presence of predisposing factors and trauma, it may invade blood vessels and gain entry into the CNS, where it can produce an acute necrotizing reaction and vascular thrombosis, including venous sinus thrombosis, especially affecting the cavernous sinus.
Externally, patients have a destructive inflammatory and necrotizing lesion affecting the face, especially in the nasal and maxillary areas.
Diabetes mellitus and diabetic ketoacidosis are major and frequent risk factors for this condition. Other predisposing conditions include malignancies, high-dose steroids, organ transplantation, immunosuppression, and iron chelation therapy (with deferoxamine).
The organisms causing this infection are mucor, rhizopus, and rhizomucor, which are fungi and not acid-fast bacilli. These fungi are seen as infrequently septated or nonseptated hyphae on histopathologic specimens.
Fungi as yeast
Cryptococcus
– Most common CNS fungal infection
– Presents as meningitis with increased ICP or mass lesion (cryptoccocoma)
– large (2-15 mm) budding yeast with a thick carbohydrate capsule (arrow)
– Often forms microabcessess.
– Predilection for the perivascular spaces
Encapsulated yeast
Histopathologic specimen demonstrates budding yeasts near blood vessels and surrounded by an inflammatory infiltrate
Seen in immunocompromised patients with CD4 count<100
S(x)s: fever, headache, neck stiffness, personality and behavioral changes, and altered mental status. Brain CT scan and MRI are performed to rule out other conditions and may demonstrate hydrocephalus, gelatinous pseudocysts, infarcts, or cryptococcomas. Lumbar puncture demonstrates an increased opening pressure, and CSF analysis shows mononuclear lymphocytosis with increased protein and low glucose levels. India ink smear is not very sensitive; however, it is useful when it is positive. Cryptococcal antigen detection in the CSF is rapid, sensitive and specific, and clinically useful, since fungal culture may take several days to weeks for a positive result to be obtained.
The initial treatment regimen is amphotericin plus flucytosine for 2 to 3 weeks. These patients should be monitored closely, since amphotericin is associated with renal failure, hypokalemia, and hypomagnesemia; and flucytosine may cause hematologic abnormalities. If the patient is doing well on amphotericin and flucytosine, or the meningitis is mild, the treatment can be switched to fluconazole 200 mg twice daily for 8 to 10 weeks. Afterward, the patient should be kept on long-term maintenance therapy with fluconazole 200 mg daily to prevent recurrences. Highly active antiretroviral therapy, by promoting immune reconstitution, plays a major role in the long-term treatment of HIV patients with cryptococcal meningitis, after the acute infection has cleared.
Mortality rate in the acute setting may be related to elevated intracranial pressure, which should be treated. Patients with increased intracranial pressure may need frequent CSF drainage by repeated lumbar punctures or even ventriculostomy.
Fungi existing as yeast
Candidiasis
Rare CNS pathogen
Presents as meningitis or abscess
Multiple yeast may connect to each other mimicking branching hyphae (pseudohyphae)
Coccidioides
Dimorphic fungi: Hyphae at 25 degrees celsius, yeast at 37 degrees celsius
Second most common CNS fungal infection usually a meningitis in normal host from Southwest
Small yeast with large spherical endospore (arrow).
Histoplasma
Rare CNS pathogen
Presents as meningitis or abscess usually in AIDS patient from Ohio or upper Mississippi Valley
Blastomyces
Rare CNS pathogen
Presents as meningitis or abscess in normal host from lower Mississippi Valley
Presents as mass lesions or less commonly a solitary lesion in deep nuclei, posterior fossa, or gray- white junction in immuno- compromised patients.
Exists in 2 forms
– Psuedocystfilledwithslow- growing round bradyzoite (circle)
– Active-growingbasophiliic comma-shaped tachyzoites
– Alsoseechronic inflammation (lymphocytes and plasma cells)
Neurocystricosis
Caused by the larval form of the pork tapeworm, Taenia solium, which is endemic in Latin America, Sub-Sahran Africa, and parts of Asia and accounts for almost 30% of epilepsy in those regions.
initially can present as an inflammatory reaction to a mass lesion
Chronically presents as seizures secondary to parenchymal calcified granulomas.
Multiple small cysts (less than 1 cm) located in parenchyma, ventricles, and basal cisterns.
Ventricular lesions can cause hydrocephalus
The punctate structure in the cyst is the scolex (arrow).
Microglial nodules
Nonspecific findings common in encephalitis
Hypercellular cluster containing microglia and reactive astrocytes (circle).
Perivascular cuffing
Nonspecific finding common in encephalitis
Lymphocytes surrounding blood vessel (arrow).
• Similar findings in demyelinating disease and CNS lymphoma
Cowdry A
Neuronal intranculear inclusions
– Single, large inclusion surrounded by a halo that efface the nucleus (circle).
– Seen in HSV, CMV, VZV, and SSPE.
Cowry B
Neuronal intranuclear inclusions
Multiple, small inclusions without a halo that do not efface the nucleus (arrows).
Seen in Polio or normally in the substantia nigra (Marinesco body)
HSV encephalitis
HSV has a predilection for the temporal lobes/ basal forebrain (circle).
Classically presents as a hemorrhagic encephalitis
Rabies
Characterized by eosinophilic intracytoplasmic inclusions within pyramidal cell neurons (Negri bodies) (circles).
Carried by:
– Raccoons
– Skunks
– Bats
– Foxes
– Coyotes
PML
Necrotic demyelination beginning in the white matter within a cortical gyrus (circle).
Characterized by:
– Ground glass inclusions in oligodendroglia nuclei (blue arrow)
– Bizzarre astrocytes (black arrow)
Bacterial meningitis by age
In order of prevalence?
Neonate: GNRs, Group B Strep, Listeria
1 mo - 15 year: H influenzae, N meningitidis, S pneumo
15 - 50 year old: S pneumo, N meningitidis, staphlococci
>50 years old: S pneumo, Listeria, GNRs
Different way to memorize it
Neonate: GNRs, Listeria, Group B Strep,
1 mo - 15 year: H influenzae, N meningitidis, S pneumo
15 - 50 year old: Staphylococci, N meningitidis, S pneumo
>50 years old: GNRs, Listeria, S pneumo
Dexamethasone in bacterial meningitis
Suggested for adults with suspected/confirmed pneumococcal meningitis, no evidence of harm in meningococcal meningitis
Best survival difference in Europeans>55
Modest reduction in hearing loss
Adds Hib meningitis in children
Dose: 10 mg q6h x 4 days
CSF Hypoglcorrhachia
Cancer
Bacterial
TB
Neurosarcoidosis
Sometimes HSV
Someties fungal
Meningococcal disease prevention if exposure
Rifampin PO 2 days, children<1 mo 5 mg/kg q12h, > 1 mo 10 mg/kg q12h, adults 500 mg q12h