intracranial lesions Flashcards
Identify each number/division.
Mesencephalon = midbrain
Diencephalon = thalamus
Telencephalon = cerebrum
**4+5 = forebrain
Describe the general pathophysiology of focal brain diseases.
Definitive dx method of each etiology for focal brain dysfunction?
Mass-type lesions that increase intracranial pressure (intracranial hypertension) and cause associated clinical signs (e.g., brain abscesses)
Neoplasia = biopsy + histopath
Inflammatory (infectious & immune-mediated) = serology, cystology/histopath
Vascular : empirical evidence, MRIs
Trauma: MRI
Dog circling in CW direction
- Left-sided proprioceptive deficit in TL
- Failed hopping in left PL
- Absent menace response on left side
- Normal palpebral and PLRs
Focal, right forebrain lesion, in the thalamus + occipital cortex
(circle ipsilateral to lesion, contralateral deficits)
How are most CNS bacterial infections caused? What is less likely?
Local infection extending into the head (oropharyngeal, otogenic, bite wounds).
Septicemia rarely causes CNS infections
IMAGE: bite wound into skull spreading into CNS // brain abscess in the telencephalon / frontal lobe
How are brain abscesses treated?
surgical drainage, 6-8 weeks broad-spectrum abx, corticosteroids
IMAGE: dog pre- and post-tx therapy
What can fungal infections in the brain cause?
Focal lesion - macrogranuloma (e.g., cryptococcus)
Granuloma = cluster of white blood cells that form as rxn to infection, inflammation, etc.
Where do primary brain tumors arise from?
resident tissues of the CNS (neurons, glial cells)
Gliomas
- tumor type / prognosis
- Origin
- Signalment
PRIMARY BONE TUMOR - INVARIABLY FATAL
- Arise from astrocytes, oligodendrocytes
- middle-aged, brachycephalic dogs
Choroid plexus tumors (CPT)
- Origin
- Signalment
- Arise from ependymal cells / inside ventricular system
- young dogs, golden retrievers+
What are the mass-related effects of focal neoplastic brain tumors?
invasion, displacement, compression, herniation
What are the secondary effects of focal neoplastic brain tumors?
Peri-tumoral edema, tumor-induced encephalitis, hemorrhage, obstructive hydrocephalus (abnormal buildup of CSF in ventricles – mesenceph. aqeduct = narrowest!)
How are brain tumors definitively diagnosed?
BIOPSY
(CSF, MRI EEG do NOT definitively dx!)
Most common “extra-axial” brain tumors? (arises from outside of the brain and pushes onto the brain, broad-based attachment)
MENINGIOMAS
- Meninges origin; since outside BBB, have propensity to have lots of contrast enhancement on MRI
Image: tumor in pons + medulla -> central vestib. signs
Most common “intra-axial” (arise from brain parenchyma) brain tumors?
GLIOMAS
- Parenchymal tissue origin; since inside BBB, typically no contrast enhancement on MRI
Image: note the lateral ventricles –> key to knowing the tumor is in the FOREBRAIN (tel or di)
What do secondary brain tumors (SBT) arise from?
Arise from tissue outside the CNS, but invade brain tissue hematogenously
Most common SBT in dog vs cat? Clinical signs?
Dog: Pituitary tumors - Cushing’s Disease // Hyperadrenocorticism (pot belly, exercise intolerance, excessive panting, PU/PD, alopecia)
Cats: Acromegaly = excess GH (widened face, enlarged feet; dullness, lethargy, blindness
What is the difference between functioning and non-functioning adenomas?
Functioning adenomas: tumors that secrete hormones
Non-functioning adenomas: do not secrete hormones
Will surgical resection cure forebrain meningiomas? What about adenomas
No- PBT will eventually return
- dogs: 10 months
- cats: >24 months
Adenomas: only 2 places in the world perform functional pituitary tumors-transphenoidal
hypophysectomy –> 86% 1 year and 68% 4-year survivals
Why is radiotherapy preferred over chemotherapy for the tx of PBTs?
Chemotherapeutic drugs often cannot pass through the BBB -> RADIOTHERAPY ROUTINELY USED IN NEURO-ONCOLOGY!
What type of disease is a stroke? What are the two types of strokes?
Cerebrovascular Disease (CVD)
1. Ischemic stroke (vasc. occlusion)
2. Hemorrhagic stroke (vasc. rupture)
What part of the brain will suffer the consequences of ischemic stroke first and why?
The GREY matter -> contains neurons
What conditions are risk factors for stroke? Why are these underlying RFs critical info?
Hypertension, pro-thrombotic conditions (PLE, PLN; Cushing’s) -> MAJOR REASON FOR RECURRING STROKES AND ASSOCIATED MORTALITY
What is the hallmark clinical sign of strokes?
Signs persist after 24 hours, but becomes non-progressive after the first 24-72 hours
How does a transient ischemic attack differ from a stroke?
TIA signs resolve after 24 hours of onset
