Читать книгу Canine and Feline Epilepsy - Luisa De Risio - Страница 249

Cerebrovascular accidents (CVAs) result from cerebrovascular disease which involves any pathological process of the blood vessels supplying the brain (Wessmann et al., 2009). CVA, also termed stroke, is characterized by non-progressive (or rapidly progressive) intracranial neurological signs with peracute (6 h) to acute (7–24 h) onset and duration of at least 24 h (Victor and Ropper, 2001). When the neurological signs last less than 24 h, the event is referred to as a transient ischaemic attack (TIA) (Victor and Ropper, 2001). TIAs may precede a CVA.

CVAs can be broadly classified as:

• Ischaemic (resulting from occlusion of a cerebral blood vessel by a thrombus or embolism, causing ischaemic necrosis or infarction); and

• Haemorrhagic (resulting from rupture of an intracranial blood vessel wall, causing haemorrhage into or around the brain) (Wessmann et al., 2009; Garosi, 2010).

Ischaemic CVA can be classified by the territory that the affected blood vessel supplies, the size of the vessel (e.g. territorial infarct with large arterial vessel disease, Fig. 5.1a–e; and lacunar infarct with small perforating arterial vessel disease, Fig. 5.2a–e), the age of the infarct (e.g. recent, organizing), the presence of secondary haemorrhage, the pathogenesis of the stroke (e.g. thrombotic, embolic, haemodynamic) and the suspected underlying aetiology.

Haemorrhagic CVA can be classified according to the anatomical site of the haemorrhage (e.g. epidural, subdural, Fig. 5.3a–d; subarachnoid; intraparenchymal, Fig. 5.4a–f; intraventricular), size of the lesion (e.g. small, large) and the age of the lesion or the suspected underlying aetiology (Wessmann et al., 2009). Several disorders can predispose to ischaemic or haemorrhagic CVA (Box 5.1).

The most commonly reported concurrent medical conditions in dogs with ischaemic CVA include hyperadrenocorticism, chronic renal disease, hypothyroidism and hypertension (Garosi et al., 2005a). Reported concurrent medical conditions in dogs with haemorrhagic CVA include Angiostrongylus vasorum infection, primary or secondary brain tumours, hypertension, hyperadrenocorticism, chronic renal disease and hypothyroidism (Lowrie et al., 2012). A concurrent medical condition has been identified in approximately 50% and 44% of dogs with ischaemic and haemorrhagic strokes, respectively (Garosi et al., 2005a; Lowrie et al., 2012).

Reports of ischaemic or haemorrhagic strokes in cats are limited (Cherubini et al., 2007; Altay et al., 2011). Reported concurrent medical conditions include hyperthyroidism, hypertrophic cardiomyopathy, hepatic and renal disease (Altay et al., 2011). The term feline ischemic encephalopathy has been used to describe cases of peracute onset of neurological signs (including seizures) consistent with a unilateral (focal) forebrain lesion caused by ischaemia associated with Cuterebra larval migration through the cerebrum. It has been suggested that the migrating parasite or the host response leads to vasospasm in the cerebral vasculature, typically the middle cerebral artery, resulting in focal cerebral ischaemia (Glass et al., 1998; Williams et al., 1998).