|
|
| (6 intermediate revisions by 3 users not shown) |
| Line 1: |
Line 1: |
| − | ==The Forebrain==
| + | {{toplink |
| − | | + | |backcolour = E0EEEE |
| − | * The nervous system can be classified functionally to:
| + | |linkpage = Nervous System - Pathology |
| − | *# The intercranial structures
| + | |linktext =Nervous System |
| − | *# The spinal cord
| + | |maplink = Nervous System (Content Map) - Pathology |
| − | *# The peripheral nervous system.
| + | |pagetype =Pathology |
| − | * The intercranial structures can be further divided into the '''rostrotentorial''' and '''caudotentorial''' structures.
| + | }} |
| − | ** The rostrotentorial structures consist of the cerebral hemispheres, basal nuclei, diencephalon and the rostral portion of the midbrain.
| + | <br> |
| − | *** Collectively, these are the forebrain.
| |
| − | * The forebrain is responsible for many functions associated with or requiring consciousness.
| |
| − | | |
| − | ==Clinical Signs==
| |
| − | | |
| − | ===Seizures===
| |
| − | | |
| − | * Seizures are a classical sign of rostrotentorial disease.
| |
| − | | |
| − | ===Altered Mentality/ Behaviour===
| |
| − | | |
| − | * The forebrain contains significant components of the limbic system, which are responsible for emotion.
| |
| − | ** Intercranial disease may therefore give rise to abnormal behaviour and aggression.
| |
| − | | |
| − | ===Circling, Head Pressing, Compulsive Walking=== | |
| − | | |
| − | * These behaviours are associated with unilateral rostrotentorial disease.
| |
| − | * There is a tendency to circle '''towards''' the side of the lesion.
| |
| − | | |
| − | ===Head Aversion===
| |
| − | | |
| − | * Head aversion is also known as head turn.
| |
| − | * Turn is usually towards the side of a unilateral lesion.
| |
| − | | |
| − | ===Menace Deficit===
| |
| − | | |
| − | * There may be a deficit in the menace response on the opposite side to a unilateral lesion.
| |
| − | ** However, the pupillary light reflex (testing optic nerve function) and facial nerve function are found to be normal.
| |
| − | * The lack of a contralateral menace response is associated with poor or absent vision.
| |
| − | ** The menace reflex is a learned response, and requires forebrain processing of visual information.
| |
| − | ** The sign is contralateral because there is significant decussation of the visual fibres at the optic chiasm in animals.
| |
| − | * There may also be a reduction in the medial visual field in the eye ipsilateral to the lesion.
| |
| − | ** This combination of visual field abnormalities is known as '''hemianopia'''.
| |
| − | | |
| − | ===Facial Sensation Deficit===
| |
| − | | |
| − | * There may be a deficit in facial sensation on the side contralateral to a unilateral lesion.
| |
| − | ** This is because CN V sends facial sensory signals to the opposite parietal cortex via the thalamus.
| |
| − | | |
| − | ===Hemiparesis===
| |
| − | | |
| − | * Hemiparesis may be a sign of forebrain disease.
| |
| − | * Many tracts cross at various levels in the CNS, however functional crossover occurs at the level of the causal mesencephalon and rostral pons.
| |
| − | ** Unilateral lesions rostral to this level give contralateral hemipareis.
| |
| − | ** Unilateral lesions caudal to this level give ipsilateral hemiparesis.
| |
| − | | |
| − | ==Differential Diagnosis==
| |
| − | | |
| − | * Remember that the age and breed of the animal are important.
| |
| − | ** Animals present with congenital abnormalities within their first year of life.
| |
| − | ** Young animals are also more predisposed to:
| |
| − | *** Infections - due to their immature immune systems and lack of vaccinations.
| |
| − | *** Intoxications - due to their innate curiosity and propensity to explore with their mouths.
| |
| − | *** Traumatic injury - due to both their curiosity and lack of road sense.
| |
| − | ** Geriatric animals tend to suffer the same kind of neurological problems as other adult animals.
| |
| − | *** Infectious, inflammatory and metabolic disorders.
| |
| − | ** Elderly animals are more likely to suffer from:
| |
| − | *** Neoplasi
| |
| − | *** Vascular problems
| |
| − | *** Degenerative disorders
| |
| − | * It must be determined whether the suspected lesion is due to a systemic disease, or to a structural change in the intracranial nervous system.
| |
| − | ** Structural change can be detected by CT or MRI scanning.
| |
| − | * The following causes must be considered and eliminated.
| |
| − | | |
| − | ===Common Diseases Affecting the Forebrain===
| |
| − | | |
| − | ====Degenerative Diseases====
| |
| − | | |
| − | * Storage diseases
| |
| − | * Cognitive dysfunction syndrome
| |
| − | | |
| − | ====Anomalies====
| |
| − | | |
| − | * Hydrocephalus
| |
| − | * Hydraencephaly
| |
| − | * Lissencephaly
| |
| − | | |
| − | ====Metabolic Diseases====
| |
| − | | |
| − | * Hepatic encephalopathy
| |
| − | ** Most commonly seen with congential liver shunts or with sever liver failure.
| |
| − | * Renal encephalopathy
| |
| − | * Pancreatic disease
| |
| − | * Glucose abnormalities
| |
| − | ** Insulinoma
| |
| − | ** Diabetes Mellitus
| |
| − | * Hypo- and hyper-thyroidism
| |
| − | * Hypoxia, for example due to:
| |
| − | ** Anaemia
| |
| − | ** Cariopulmonary disease
| |
| − | ** Severe URT obstruction
| |
| − | * Hypertension
| |
| − | * Ion inbalances
| |
| − | ** Hypocalcaemia
| |
| − | ** Hypokalaemia
| |
| − | *** For example in chronic renal failure or hyperaldosteronism
| |
| − | ** Hypophosphataemia
| |
| − | ** Hypomagnesaemia
| |
| − | *** E.g. in hepatic lipidosis or re-feeding syndrome.
| |
| − | | |
| − | ====Neoplasia====
| |
| − | | |
| − | * Primary brain tumours
| |
| − | * Metastatic tumours
| |
| − | * Local extension of tumours
| |
| − | | |
| − | ====Nutritional Conditions====
| |
| − | | |
| − | * Thiamine deficiency
| |
| − | | |
| − | ====Infectious Causes====
| |
| − | | |
| − | * Canine distemper
| |
| − | * FIP
| |
| − | * Toxoplasmosis
| |
| − | * Fungal disease
| |
| − | * Rickettsial diseases
| |
| − | * Rock Mountain spotted fever
| |
| − | * Ehrlichia
| |
| − | * Bacterial infections
| |
| − | * Parasitism
| |
| − | | |
| − | ====Trauma====
| |
| − | | |
| − | * Head trauma
| |
| − | | |
| − | ====Toxicity====
| |
| − | | |
| − | * Metranidazole
| |
| − | * Lead
| |
| − | | |
| − | ====Vascular====
| |
| − | | |
| − | * Arteriovenous malformation
| |
| − | * Infarction
| |
| − | * Feline ischaemic encephalopathy
| |
| − | * Haemorrhage
| |
| − | * Hypertension
| |
| − | | |
| − | ==Diagnosis==
| |
| − | | |
| − | * Diagnosis must encompass the following:
| |
| − | | |
| − | ===History===
| |
| − | | |
| − | * Aside from the normal history, there are several very important questions to be asked:
| |
| − | ** Has there been any possible exposure to toxins or trauma?
| |
| − | ** What is the animal's diet?
| |
| − | ** Are the litter mates normal?
| |
| − | ** Are there any specific clinical signs that may relate to a particular diagnosis?
| |
| − | ** E.g. hypersalivation - commonly seens in young animals with portosystemic [[Liver - Anatomy & Physiology|liver]] shunts.
| |
| − | | |
| − | ===Physical Examinations=== | |
| − | | |
| − | * Check for signs of systemic disease.
| |
| − | ** Ocular changes with FIP, toxoplasmosis, FeLV or lysosomal storage diseases.
| |
| − | ** Ascites with with FIP, liver or cardiac disease.
| |
| − | | |
| − | ===Neurological Examination===
| |
| − | | |
| − | * This should include CN examination, postural reactions, spinal reflexes and sensory examination.
| |
| − | | |
| − | ===Blood and Urine Tests===
| |
| − | | |
| − | * Blood tests should include haematology and serum biochemistry.
| |
| − | * These are particularly helpful in the diagnosis of many systemic and especially metabloic conditions.
| |
| − | | |
| − | ===Infectious Disease Tests===
| |
| − | | |
| − | * E.g. FeLV and FIV, toxoplasma [[IgM]] and [[IgG]] tests.
| |
| − | | |
| − | ===CSF Analysis===
| |
| − | | |
| − | * Particularly useful in the diagnosis of:
| |
| − | ** Inflammatory diseases
| |
| − | *** E.g. FIP
| |
| − | ** Lymphoma
| |
| − | | |
| − | ===Imaging===
| |
| − | | |
| − | * Radiographs of the chest and abdomen
| |
| − | * Abdominal ultrasonography
| |
| − | * MRI or CT scans
| |
| − | ** Examine the structure of the brain and determine presence or absence of inflammation or neoplasia.
| |
| − | | |
| − | [[Category:Central Nervous System - Pathology]]
| |
