Case Report CT Scan Features of Presumptive Haemorrhagic Stroke in a Dog with Cushing's Disease 2 Case Reports in Veterinary Medicine Conflict of Interests

A 9-year-old, intact male, Brie's shepherd dog, with a 10-day history of depression and tachypnoea developed signs of central neurological dysfunction. 16 Multislice Computed Tomography (CT) pre-and postcontrast studies of the brain revealed a single intra-axial homogeneous well-circumscribed hyperattenuating (+/− 62 HU) and noncontrast-enhancing area, 5 mm in diameter, in the caudal part of the mesencephalon. This finding was highly suggestive of a haemorrhagic event. A pituitary-dependent hyperadrenocorticism (PDH) was identified and is considered likely to be the underlying cause. A repeat CT scan examination, 2 months later, showed almost complete resolution of the brain lesion. The present case describes a solitary 5 mm diameter lesion: the result of intracranial haemorrhage in a dog with presumed PDH. Case Presentation A 9-year-old, entire male, Brie's shepherd dog, was referred with a 10-day history of acute depression and tachypnoea. On clinical evaluation, the only abnormalities detected were obtundation and superficial tachypnoea. A complete blood count, biochemistry profile, blood gas analysis, and urinalysis revealed only a mild increase in serum GGT, ALT, and cholesterol. Systolic blood pressure (Doppler method) was within normal limits. Thoracic radiographs were unremarkable. Three days later, the dog developed acute neurological signs consistent with central dysfunction with right-sided amaurosis, ventromedial strabismus of the left eye, and leftsided Horner's syndrome. 16 Multislice Computed Tomography pre-and postcontrast studies of the brain were performed. A single intraaxial, homogeneous, well-circumscribed, irregularly shaped, hyperattenuating (+/− 62 HU), and noncontrast-enhancing area of 5 mm diameter was observed in the caudal part of the mesencephalon, mildly left-sided, exerting a mild mass effect on the surrounding structures and associated with dilation of the ventricular system Two months after initial presentation the patient was lost to follow-up. Discussion Diagnosis of intracranial haemorrhage is based on CT and MRI: the former is very sensitive and was previously the primary diagnostic tool for detection of haemorrhage in human medicine. MRI provides a more accurate estimate of the stage of haemorrhage by identifying sequential patterns of degradation of the haemoglobin molecule during haematoma transformation There is a linear relationship between CT attenuation, protein content (mainly haemoglobin), and haematocrit. In the early hours of haemorrhage, the lesion exhibits moderate high-density values, because of freshly extravasated blood characterized by cells interspersed with protein-rich serum. The increase of haematocrit in the subsequent period gives the lesion the aspect of a well-demarcated hyperattenuated lesion, with Hounsfield units' values reaching 60-80 HU. With clot retraction the CT attenuation values increase to 80-100 HU in the centre of the haematoma, while a hypoattenuating halo surrounds the central nidus due to serum extrusion and reactive vasogenic oedema. In the weeks following the acute event the attenuation of the haematoma decreases as proteolysis begins, even if the mass effect persists. Within weeks or months, the digestion of blood degradation products by macrophages can lead to the total resolution of the lesion, even if calcification, hypoattenuating area, focal atrophy, or ventricular enlargement can be easily detected on CT images and can represent the sequel of an old haematoma Primary intracranial haemorrhage is less frequent than secondary intracranial haemorrhage and is considered very rare in animals In the present case, the pituitary gland appeared within normal limits on CT examination, but one limitation is that a dynamic CT examination was not performed. However, even if dynamic CT provides very useful information in additional to conventional contrast-enhanced CT, the absence of abnormalities on dynamic CT examination does not rule out the presence of a microadenoma Case Reports in Veterinary Medicine 3 The incidence of HAC in dogs with intracranial haemorrhage is at present unknown. In a study of Garosi et al. [15], HAC was cited as a potential underlying cause of cerebrovascular accident in dogs, but all reported cases involved ischaemic infarction. In another study The absence of histological confirmation for both the suspicion of intracranial haemorrhage and the pituitarydependent HAC represents a limitation in this case. However, the resolution of the lesion on the second CT examination and the absence of clinical signs two months after the event support our suspicion of intracranial haemorrhage. On the other hand given the positive low-dose dexamethasone suppression test and the bilateral increase in adrenal gland size we can postulate that pituitary-dependent HAC is the most likely underlying disease, although this diagnosis could not be confirmed. In conclusion, the present case describes an intracranial haemorrhage in a dog with suspected Cushing's disease as a single lesion of 5 mm diameter