Introduction
Brain ischemic stroke is increasingly recognized in canines through more widespread. Diagnosis requires modern brain imaging and sometimes cannot be diagnosed in time, and the consequences are paresis, paralysis, or death. The symptoms of this disease depend on the location and severity of the lesion. Dogs may experience head pressure ataxia, circling, or seizures. Some dog has an ischemic in the brain that is not up to 24 hours is similar to what people call temporary ischemic which is difficult to diagnose and not be able to know the cause of the disease.
Brain ischemic stroke occurs when the blood supply to a part of the brain is disrupted. Oxygen and glucose cannot be delivered to the brain, causing brain cells to die. Blood flow can be compromised by a variety of mechanisms, such as occlusion of the lumen by a thrombus or embolus, rupture of the blood vessel wall, lesion or change in the permeability of the vessel wall, and increased viscosity or other changes in the blood [1,2,3]. Lesions affecting cerebral blood vessels are divided into 2 broad categories: ischemia with or without infarction due to blood vessel obstruction and hemorrhage caused by blood vessel rupture. Most dogs are often a brain from stroke constricted which causes other diseases, such as hypertension, chronic renal disease, hyperglycemia, diabetes mellitus, hyperthyroidism or hypothyroidism, and Cushing’s disease.
Imaging strategies for ischemic stroke assessment have become a requisite component of neurological examination. Imaging studies of the brain are necessary to rule out other causes of causes-onset neurological signs and to confirmion of ischemic stroke [4]. The imaging goals in ischemic stroke address whether an ischemic stroke is a likely diagnosis, whether the primary process is ischemic or hemorrhagic, the location of the lesion, the potential treatments, and the prognosis. Advanced computed tomography (CT) techniques, which are increasingly available in veterinary practice, have led to new alternatives for non-invasive brain CT imaging, even in small animals [5]. CT has improved greatly over the last decade due to the development of multidetector CT, which is faster and allows for the acquisition of studies, such as CT perfusion and CT angiography, in a reliable way.
However, only a few studies on CT findings in dogs with suspected stroke have been published in veterinary medicine. Furthermore, no reports have demonstrated CT Hounsfield Units (HUs), histograms, and volumetric measurements of the 4 arteries of the brain (rostral cerebral artery, middle cerebral artery, caudal cerebral artery, and caudal cerebellar artery) in suspected stroke dogs. The objective of our study was to determine the clinical characteristics and quantitated CT images in terms of volume and histogram analysis of the ROIs (rostral cerebral artery, middle cerebral artery, caudal cerebral artery, and caudal cerebellar artery) in dogs with suspected stroke. We described the clinical syndromes in dogs with suspected stroke, affected brain regions, and quantitated CT images of several parameters.
Materials and Methods
Animals
Three healthy dogs and six suspected ischemic stroke dogs were collected from Prasuarthorn Animal Hospital and Kasetsart University Veterinary Teaching Hospital, Bangkhen Campus, Bangkok, Thailand. The dogs consisted of six males and three females ranging in age from 7 months to 13 years and weighing between 10 and 28 kg. The Animal Ethics Committee of the Faculty of Veterinary Science, Mahidol University of Thailand (MUVS-2015-05-19).
The healthy dogs (control group) were obtained from a dog volunteer from the Prasuarthorn Animal Hospital. They must have good health, be of all genders, be aged less than 6 years, not have a history of nervous system signs and the results of the physical and neurological examinations are normal.
The group of suspected stroke dogs consisted of all ages and sexes, and they exhibited weight gain of >10 kg and a history of nervous system signs in intracranial diseases, such as circling walk, head pressing, head tilt, crossed eyes, weakness, ataxia, paralysis, and seizure within 30 days. The owner has been brought to maintain the nervous system disease at Prasuarthon Animal Hospital or Kasetsart University Veterinary Hospital Bangkhen. The dog of the caring diagnosis assumes that an ischemic stroke is from the database. History of dogs with the nervous system, such as circling walk, head pressing, head tilt, crossed eyes, weakness, ataxia, paralysis, seizure, and after neurological examination found problems in the brain by animals with acute (shown symptoms of more than 6 hours after a lack of blood ) or extreme acute (shown symptoms within 6 hours after a lack of blood) [6] and later the symptoms do not have more serious problems or have better in order from the fault of the nervous system (a one time or intermittently occurred). The dogs have both a history of treatment and do not have a history of treatment.
Clinical studies
Clinical, neurological, and blood examinations were performed at the Prasuarthon Animal Hospital of Mahidol University. Blood examination included complete blood count and serum biochemistry (blood urea nitrogen), creatinine, alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase).
Computerized tomography
The animals were under general anesthesia throughout the procedure. General anesthesia was inducted with propofol 5 mg/kg, intravenous (IV) injection. Then, the patient is maintained with 2% isoflurane and 100% oxygen, and intravascular fluid is provided with an acetate ringer at 5 ml/kg/h. The dog was then placed in the dorsoventral position. Pulse rate, respiratory rate, and the response of the nervous system (palpebral reflex and muscular reflex) were monitored during the procedure.
CT examinations were performed using (optimums 64 slice, GE) was used for cerebral angiography, and a pre-contrast helical scan was performed from the head to the thorax in the rostral to caudal direction to determine the position of the bolus-tracking site and CTA. The trigger threshold for bolus tracking was set at 110 HU. A plain, non-contrast study of the brain was performed immediately followed by a post-contrast study after the administration of Iohexol at a dose of 600 mg iodine per kilogram as a rapid intravenous bolus. The contrast medium was injected at a rate of 2 ml/second using a contrast injection system, and the contrast injection pressure was recorded. CT brain angiography was automatically initiated at the occipital bone level in the caudal to rostral direction with a 7–15 sec delay. The parameters were as follows: 120 kV, 200 mA, rotation time of 0.5 second/rotation, pitch factor of 0.938, and scan thickness of 0.125 mm. The reconstruction parameters were: slide thickness of 0.625 mm with the standard algorithm.
Radiologist veterinarians check a dog with CT. A healthy dog will check with a CT machine to use to determine the differences between each species the scan is intended to review the vascular in the brain that appears in the image of the contrast agent in the normal dog and has the disease [7].
Quantitative computed tomography measurements
CT Hounsfield units of the ROI
The CT HU defined the density of the 4 arteries including: the rostral cerebral artery, middle cerebral artery, caudal cerebral artery, and caudal cerebellar artery. The HU of the vessels was calculated using axial images, and round ROIs were placed within the segment closest to the circle of Willis; these locations were also uniformly applied for qualitative analysis.
CT-based histogram analysis of ROI
Histogram analyses of the 4 arteries are the same as HU. The ROI was determined by manually tracing the left and right arteries using Dicom Viewer (OsiriX, The OsiriX Foundation, Geneva, Switzerland). The total mean histogram of the regions was calculated for each slice in all dogs. For further analysis, the histogram of each artery was normalized against the total vessel histogram of the same dog [(histogram of vessel/histogram of total vessels) x100].
CT-based volumetric measurement
For quantitative analysis, VOIs were manually drawn over dorsal (coronal) slices using Dicom Viewer (OsiriX, The OsiriX Foundation, Geneva, Switzerland). CT images were used as anatomical reference. The bilateral VOIs covered 4 arteries including: rostral cerebral artery, middle cerebral artery, caudal cerebral artery, and caudal cerebellar artery (Fig. 1A–D). The VOIs were calculated as the sum of the volumes obtained by multiplying the area of each slice (cm2) by the slice interval (cm). The slice interval is the sum of the slice thickness and slice gap. The volumes of the left and right arteries were calculated.
Statistical analysis
The statistical analysis was performed using IBM SPSS software version 21.0 (Armonk, NY). For the control and suspected dogs, the median age and body weight were calculated. The mean and standard deviation were calculated for HU, histogram, and volumetric analyses of 4 arteries. We compared the suspected and control groups using the Mann–Whitney U-test. Statistical significance was set at a p-value < 0.05.
Results
Clinical characteristics and ischemic stroke dogs
The nine dogs were performed with a CT scan. Three healthy and six ischemic stroke dogs met the inclusion criteria; one of five symptoms; including head tilt, Ataxia, Weakness, Seizure, and circulation. There were six mixed breeds, two Poodle, and one Siberian husky (totally, nine dogs included six males and three females). The median age at presentation of dogs was 4 years (range: 7 months-13 years 10 months of age). General the general regarding factors associated with ischemic stroke are presented in
Neurological examinations were performed on nine dogs. Evaluation of the nervous system begins with history taking, physical examination, and neurological examination. These included tests of the cranial nerve, spinal reflexes, muscle function, postural reaction, and gait. Overall clinical examinations were found revealed, ataxia, seizure, head falling of the head, head turn, ataxia, and circ, and in each individual ischemic stroke dog. In the neurological examination, the most common was seizure and the others are presented in Table 1.
Figure 1.
The regions of interest (ROI) in dogs are the rostral cerebral artery (A), the left and right middle cerebral artery (B), the left and right caudal cerebral artery (C), and the left and right caudal cerebellar artery (D).
CT findings
This study demonstrated CT imaging of whole brain lesions in dogs. There were abnormal areas in dogs with suspected stroke. CT imaging detected brain changes in several regions, including the frontal (1/6 dogs), thalamus (1/6 dogs), and pituitary (1/6 dogs). CT images presented in dogs with suspected ischemic stroke, as shown in Figure 2. The neurological findings are useful in predicting whether results CT results are abnormal in dogs examined because of ischemic stroke.
Quantitative CT
CT Hounsfield units, histograms, and VOIs of 4 arteries including: rostral cerebral artery, middle cerebral artery, caudal cerebral artery, and caudal cerebellar artery were evaluated.
Table 1.
Summary of clinical characteristics performed on three healthy and six suspected stroke.
| No. | Sex | Breed | Ages (m) | Weight (kg) |
Clinical examination | Neurologic examination | Diagnosis |
|---|---|---|---|---|---|---|---|
| 1 | F | Mixed | 7 | 15 | Normal | Normal | Healthy |
| 2 | M | Mixed | 24 | 16 | Normal | Normal | Healthy |
| 3 | M | Poodle | 7 | 15 | Normal | Normal | Healthy |
| 4 | M | Mixed | 20 | 13 | Seizure Ataxia |
Menace 1+ ProprioceptivE 1+ Placing 1+ |
Hemorrhagic ischemic stroke |
| 5 | F | Poodle | 90 | 10 | Vertical Nystagmus Rt headtilt Ataxia Vomiting |
Menace OS + OD- Placing 2+ ProprioceptivE 2+ |
Suspected ischemic stroke |
| 6 | M | Mixed | 156 | 18 | Seizure Paresis |
Menace 0 Cotton ball: Dazzle - PLR 2+ |
Suspected ischemic stroke |
| 7 | M | Siberian Husky | 48 | 24 | Seizure | ProprioceptivE 2+ Menace 2+ PLR 2+ |
Suspected ischemic stroke |
| 8 | M | Mixed | 29 | 14 | Seizure | Menace 1+ ProprioceptivE 2+ PLR 2+ |
Suspected ischemic stroke |
| 9 | F | Mixed | 166 | 28 | Lt headtilt Nystagmus Ataxia Vomit |
Menace1+ ProprioceptivE 2+ PLR 1+ |
Suspected ischemic stroke |
F=female, M=male, Lt=left, Rt=right, m=month.
CT hounsfield units of the ROI
The mean HU value of the left and right caudal cerebellar artery in dogs with suspected stroke had a significantly higher density than that of control dogs, as shown in Table 2. However, the rostral cerebral artery did not change in HU values. This result demonstrated that the left and right caudal cerebellar artery, middle cerebral artery, and caudal, and cerebral artery of suspected ischemic stroke dogs were hyperdensity compared with those of control dogs.
CT-based histogram analysis of ROI
The mean histogram of four arteries of the brain including; the rostral cerebral artery, middle cerebral artery, caudal cerebral artery, and caudal cerebellar artery, are shown in Table 2. The group of dogs with suspected ischemic stroke also showed a significantly higher mean histogram of the right middle cerebral artery than the control dogs. This result was related to the results of CT Hounsfield units, which showed that the caudal cerebral artery and caudal cerebellar artery tended to increase in density in dogs with suspected stroke.
CT-based volumetric analysis
The group of dogs with suspected stroke tended to increase in the volume of the two arteries of the brain including; the caudal cerebral artery and the caudal cerebellar artery, although the effect was not statistically significant, as shown in Table 2. No significant difference was observed in the two arteries (rostral cerebral artery and middle cerebral artery) compared with the healthy dogs. We found lesions in 4/6 dogs with suspected stroke can cause congestion due to preferential compression of the arteries. Because blood has a high density, congestion may increase brain density. In our study, changes in the density of arteries were observed in the group of dogs with suspected stroke. However, only one dog was in the group of suspected strokes (1/6) that was hemorrhagic stroke (Fig. 2B and D).
Figure 2.
CT images of the lesion of the brain in transverse view (A) healthy dog and (B) suspected stroke dog. (C) CT image in sagittal view of healthy dog and (D) suspected stroke dog.
Discussion
The present study describes the clinical characteristics, for the first time to our knowledge, of quantitative CT imaging in several arteries using OsiriX software in stroke dogs. CT is often scanned as an initial screening tool to discourage in humans with patients suspected of ischemic stroke. Established areas of infarction present as elusive hypodense lesions on CT owing to the influx of water associated with cerebral edema [8]. CT was previously scanned as the primary diagnostic tool for the detection of ischemic stroke patients. A hematoma appears as a firm, homogeneously hyperdense image, whereas petechial hemorrhages appear as hyperdense points, which may combine with an irregular hyperdense area [9]. The lesion appears isodense with variable contrast enhancement. In our study, we found lesions in dogs with suspected stroke on CT images, and the density of arteries was significantly increased compared with the control dogs. The results suggested that the rostral cerebral artery and caudal cerebellar artery may change when compared with normal dogs.
A previous study described the pattern of canine thalamic nuclei anatomy between ischemic stroke lesion distribution and outcome [10]. The neurological deficits associated with lesions at different sites were characterized. Dogs with paramedian infarcts mainly had vestibular dysfunction; those with ventrolateral lesions showed circling and contralateral proprioceptive deficits; and those with dorsal general lesions presented with ataxia, circling, and contralateral menace deficits. In our study, dogs with suspected ischemic stroke had ataxia, circling, proprioceptive deficits, and contralateral menace deficits. CT images showed lesions at the frontal, thalamus, and pituitary.
Table 2.
The HU, histogram, and volumetric of four arteries in healthy and suspected ischemic stroke dogs.
| Vessels | Side | HU | Histogram | VOI | |||
|---|---|---|---|---|---|---|---|
| Normal | Suspected ischemic stroke | Normal | Suspected ischemic stroke | Normal | Suspected ischemic stroke | ||
| Rostral cerebral artery | 139.7 ± 13.5 | 175.9 ± 8.2 | 13.92 ± 0.36 | 13.9 ± 0.20 | 4.57 ± 0.96 | 3.92 ± 1.69 | |
| Middle cerebral artery | Lt | 141.9 ± 25.5 | 136.4 ± 19.3 | 13.98 ± 1.20 | 15.21 ± 1.45 | 3.19 ± 0.7 | 2.96 ± 1.3 |
| Rt | 146.0 ± 12.4 | 145.0 ± 28.5 | 13.92 ± 0.36 | 15.21 ± 1.31* | 3.56 ± 1.14 | 3.13 ± 1.52 | |
| Caudal cerebral artery | Lt | 169.8 ± 18.0 | 149.2 ± 31.2 | 15.48 ± 0.84 | 14.89 ± 1.69 | 4.71 ± 4.28 | 7.1 ± 3.7 |
| Rt | 161.4 ± 21.0 | 152.6 ± 17.8 | 14.82 ± 0.48 | 13.96 ± 0.20 | 5.95 ± 0.53 | 6.30 ± 3.37 | |
| Caudal cerebellar artery | Lt | 119.9 ± 3.0 | 155.0 ± 10.1* | 14.11 ± 0.93 | 15.05 ± 1.42 | 3.07 ± 1.47 | 4.16 ± 2.44 |
| Rt | 121.2 ± 8.0 | 151.1 ± 6.6* | 13.98 ± 1.57 | 15.38 ± 1.21 | 2.64 ± 2.66 | 4.39 ± 2.89 | |
Lt=left, Rt=right.
Values are the mean ± SD.
*Significant differences were denoted by the same letter, p < 0.05.
D-dimer determination and antithrombin III levels are useful screening tests to include in routine coagulation profiles, along with prothrombin time, activated partial thromboplastin time, and fibrinogen degradation products. Preliminary veterinary studies have shown the potential for the use of D-dimer to screen for disseminated intravascular coagulation and thromboembolic disease. Our study showed that dogs with ischemic stroke had low D-dimer concentrations <45 ng/ml. There was no difference between the two groups. Maybe this technique is not sensitive to dogs.
In stroke, perfusion CT offers fast and reliable identification of stroke signature; improved choice of treatment modality, including exclusion of patients from thrombolytic therapy; pinpointing the vascular origin of ischemic insult; and determination of neurological consequences of the stroke, including final infarct size, clinical outcome, and hemorrhagic risk. In acute stroke, blood flow in the brain leads to various cerebral perfusion disturbances. The feasibility of using a computed tomography (CT) scanner to measure cerebral blood volume was first discussed [11]. Unfortunately, the CT that we used in this project had not the software for determining brain perfusion. Therefore, we quantitated brain lesion imaging using the Osirix software.
Because routine CT scans only showed hypodensity and hyperdensity in some areas of the brain. In this study, we performed quantitative CT including HU, histogram, VOI, and VOI, in vessels of the dogs and suspected ischemic stroke. The VOI can be used to calculate the volume of blood vessels in the arteries. The results showed that the volumes of the caudal cerebral and cerebellar arteries tended to increase. Histogram analyses of the middle cerebral artery and caudal cerebellar artery in dogs with suspected stroke also showed a trend to increase, which indicated that these arteries demonstrated hyperdensity in dogs with suspected stroke compared with control dogs. In addition, data on the HU values of the cerebellar artery showed a statistically significant difference between normal and suspected ischemic stroke dogs. However, the HU values of the arteries in our control groups were the same as the CT attenuation values in healthy beagle dogs [12]. Finally, our study is limited to six dogs with suspected ischemic stroke, and only one dog had a hemorrhagic stroke. The number of dogs was small. Future studies are needed to determine whether our results can be confirmed in larger samples.
Conclusion
The study result showed CT abnormalities in several brain regions, revealing hyperdensity in dogs with suspected stroke. In addition, we performed quantitative CT including HU, histogram, VOI, and VOI, in the vessels dogs, and the results that those changes infected ischemic stroke dogs. These findings suggest that the diagnostic yield of CT, which is the alternative technique in detecting abnormal areas in suspected ischemic stroke dogs, is faster, noninvasive, and has a low cost. It can be used to identify lesions in the brain of dogs with suspected stroke, which helps in the formulation of treatment plans and determining prognosis.
List of abbreviations
CT, Computed tomography; HU, Hounsfield unit; VOI, volume of interest; IV, intravenous; ROI, region of interest; SD, standard deviation.
Acknowledgment
This study was supported by a grant from the Faculty of Veterinary Science, Mahidol University.
Conflict of interests
The author declares any conflict of interest.
Authors’ contribution
This study was accomplished with the participation of all authors. SH designed the study, selected a case study, and conducted the experiment. PY analyzed the data, designed the analysis results, performed quantitative CT imaging, performed statistical analysis, and prepared the manuscript. WT scan CT. TM, IA, and DC did data collection and analyzed the hematological and biochemical parameters. The authors have approved the manuscript.
Ethical approval
The Animal Ethics Committee of the Faculty of Veterinary Science, Mahidol University of Thailand (MUVS-2015-05-19).
Statement of novelty
This paper studies quantitative CT images and computed tomography images, including Hounsfield units, histograms, interest of arteries of interest of canine suspected ischemic stroke.
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