Evaluation of Hydrocephalic Ventricular Alterations in Maltese
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Evaluation of Hydrocephalic Ventricular Alterations in Maltese Dogs Using Low Field MRI Jung-Woo Nam, DVM1* Chi-Bong Choi, DVM, Ph.D2* 3 Dong-Cheol Woo, Ph.D 2 Kyung-Nam Ryu, MD, Ph.D 1 Eun-Hee Kang, DVM 1 Hwa-Seok Chang, DVM 3 Do-Wan Lee, Msc 3 Bo-Young Choe, Ph.D 1 Hwi-Yool Kim, DVM, Ph.D. 1Department of Veterinary Surgery, College of Veterinary Medicine, Konkuk University, #1 Hwayang-Dong, Kwangjin-Gu, Seoul, Republic of Korea 2Department of Radiology, Kyunghee University Medical Center, Hoeki-dong, Dongdaemun-gu, Seoul 130-702, Republic of Korea 3Department of Biomedical Engineering, Research Institute of Biomedical Engineering, College of Medicine, The Catholic University of Korea, Seoul, Republic of Korea * The first two authors contributed equally to this study. KEY WORDS: Hydrocephalus, ventricles, brain sizes. Five symptoms were observed magnetic resonance imaging, Yorkshire in the hydrocephalic group: circling, head terrier tilt, seizure, ataxia, and strabismus. The ABSTRACT ventricle/brain with height (1D) was linear relative to the area (2D) and volume (3D). The purpose of this work to evaluate quantitatively ventricular alterations of Its correlations with area and volume were hydrocephalic Maltese dogs using low-tesla as good as the ventricle/brain height ratio MRI. The height, area, and volume of the in case of hydrocephalic dog. Therefore, ventricles and brain were measured in 40 one-dimensional, two-dimensional, and Maltese (20 normal and 21 hydrocephalic three-dimensional quantitative methods may dogs) on MR images (at 0.2T MRI). All of be complementary. We expect that the stage the relative ventricle sizes were defined as of hydrocephalic symptoms can be classified the percent size of the ventricle/size of the if statistical significance for ventricular size brain. The ventricle sizes of hydrocephalic among symptoms is determined with the dogs were significantly larger than the analysis of a large number of hydrocephalic normal dogs, as were the relative ventricle- cases. 58 Vol. 9, No. 1, 2011 • Intern J Appl Res Vet Med. InTRoduCTIon Magnetic resonance (MR) imaging is com- Hydrocephalus is affected by blockage of monly used to evaluate companion animals cerebrospinal fluid (CSF) outflow in the ven- for suspected central nervous system (CNS) tricles or in the subarachnoid space over the disease. Many studies in the autism lit- brain. Alternatively, the condition may result erature have utilized MRI as a method for from an overproduction of CSF fluid, from studying volumetric differences in the brains a congenital malformation blocking normal of autistic subjects vs those of typically de- drainage of the fluid, or from complica- veloping children. Reports from such studies 10 tions of head injuries or infections.1-3 This include an increase in total brain volume condition also could be termed a hydrody- and cerebellar and parietal lobe abnormali- 11 namic disorder of CSF. Acute hydrocephalus ties. MRI has also proved to be a sensitive occurs over days, subacute hydrocephalus tool for assessing white matter changes and 12, over weeks, and chronic hydrocephalus over cerebral atrophy both in living subjects 13 14 months or years. as well as in the post-mortem brain in There are three classes in hydrocephalus. disorders such as Alzheimer’s disease. In ad- First, normal pressure hydrocephalus (NPH) dition, MRI have used to evaluate quantita- tively in the veterinary diagnosis and many describes a condition that rarely occurs in 15-17 comparatively young patients. Enlarged ven- animal studies. tricles and normal CSF pressure at lumbar Various studies for the measurement of puncture (LP) in the absence of papilledema the hydrocephalic ventricle in canine breeds led to the term NPH.4 have been attempted using CT/MRI and so- 18-20 Secondly, benign external hydrocepha- nography. The imaging modalities have lus is a self-limiting absorption deficiency been generally processed by analysis of only of infancy and early childhood with raised the morphology such as the ventricle size intracranial pressure (ICP) and enlarged and volume. It has been reported that the ra- subarachnoid spaces. The ventricles usually tio of the ventricle height to brain height was are not enlarged significantly, and resolution 80% (reference range, 0–14%) and the ratio within 1 year is the rule.5 of the ventricle area to the hemisphere brain was 7.1% (normal range, 3.0–7.6%).15, 16 The third, communicating hydrocephalus occurs, when full communication occurs In humans, the correlation between ven- between the ventricles and subarachnoid tricular height and volume is as good as the space. It is caused by overproduction of ventricle/brain ratio, which has previously been shown to be the best non-volumetric CSF, defective absorption of CSF, or venous 21-23 drainage insufficiency.6 correlate of ventricular volume. How- ever, in canines, an evaluation and compari- Forth, noncommunicating hydrocephalus son of the analysis methods have not yet occurs when CSF flow is obstructed within been reported. Therefore, we hypothesized the ventricular system or in its outlets to the that the analyzed result by the area/volume arachnoid space, resulting in impairment of of brain and ventricle could discriminate as the CSF from the ventricular to the sub- accurate as by their heights between normal arachnoid space.7 and hydrocephalic canine. The final purpose Lastly, congenital hydrocephalus applies of present study was to evaluate quantita- to the ventriculomegaly that develops in tively ventricular alterations of hydrocephal- the fetal and infancy periods, often associ- ic Maltese dogs using low-tesla MRI. ated with macrocephaly. The most common causes of congenital hydrocephalus are MATERIALS And METHodS obstruction of the cerebral aqueduct flow, AnimalsForty one Maltese dogs (0–5 years; Arnold-Chiari malformation, or Dandy– 21 dogs with hydrocephalic symptoms Walker malformation.8, 9 and 20 healthy dogs) were used in the study without sex discrimination. All of Intern J Appl Res Vet Med • Vol. 9, No. 1, 2011. 59 the symptoms of each hydrocephalic dog brain sizes of the canines were different, the were recorded, and the age-matched dogs VOI covered changing slice thicknesses and without any symptoms were involved for number of slices. Figure 1 shows representa- the comparison study between normal and tive T1-weighted axial images of normal and hydrocephalic dogs. This study was ap- hydrocephalic Maltese dogs at the level of proved by the Institutional Animal Care and the interthalamic adhesion. Use Committee at the College of Veterinary Data Analysis Medicine, Konkuk University (IACUC No.: T1-weighted MR images were analyzed KU09047). All of the dogs without symp- across a series of regions of interest (ROI) as toms were considered normal following illustrated in Figure 2. Figure 2A shows that a physical and hemodiagnostic (complete the height (mm) of the brain and height of blood count) examination and determination the right and left ventricles was measured. In of blood chemistry. Diagnosis of the dogs order to measure the areas, (Figure 2B) and was performed at the Doctor’s Pet Hospital volumes (Figure 2C) of the whole brain and in Seoul, Korea, over a 5-year period (from left and right ventricles, each section was 2004 to 2009). Although blood physical/ extracted on all T1-weighted MR images. chemical examinations--complete blood These results present the height as “mm,” count (CBC), total protein (TP), aspartate the area as “mm2” and the volume as “mm.3” aminotrasferase (AST), alanine amino- The height and areas of the brain and both trasferase (ALT), blood urea nitrogen (BUN) ventricles were measured at the level of the and creatinine (CREA)--were performed. All interthalamic adhesion. The transverse im- values indicated healthy condition, and the age at the level of the interthalamic adhesion difference between dogs with and without was used to identify the onset of ventricu- symptoms was also not significant. lar expansion. Although in some puppies TREATMEnT And dATA ACQuISITIon the rostral horns dilated first, ventricular The MR scan of the clinical patient was per- expansion by cerebrospinal fluid (CSF) was formed under general anaesthesia. Following most apparent at this level first. The onset of prermedication with butorphanol at a dose ventricular expansion was defined as the day rate of 0.2 mg/kg body weight, the animal that expansion by CSF was first visible in received propofol at a dose of 5 mg/kg body unilateral or bilateral lateral ventricles on the weight. Then it was intubated and con- above transverse image. The pattern of onset nected to a closed-system anaesthetic unit to of ventricular expansion was also evaluated provide the animal with oxygen, while the by inspection on the transverse image at the propofol dose was doubled. Rocuronium at a level of the intraventricular foramen. dose of 0.6 mg/kg body weight was applied As a next step, the ventricle to brain as a muscle relaxant. height ratio (VBHR, ventricle height/brain MR experiments were conducted using height × 100), the ventricle to brain area open magnet MRI at 0.2T (E-scan, Esaote, ratio (VBAR, ventricle area/brain area × Genoa, Italy) with human knee coils. Dogs 100) and the ventricle to brain volume ratio were placed in sternal recumbency on the (VBVR, ventricle volume/brain volume × scanning table. Transverse and dorsal T1- 100) were calculated. Last, the comparison weighted MR images were acquired using between VBHR and VBVR as well as the a repetition time (TR) of 650 ms and an difference between normal dogs and dogs echo delay time (TE) of 25 ms. The slice with hydrocephalus were investigated. thickness was 4–6 mm, with no gap.The Statistical analysis total thickness of images was 4 cm. A total All of the data was analyzed using ImageJ of 6–8 MR image slices were used, with a (National Institutes of Health, Bethesda, MD volume of interest (VOI) that covered from USA) and SPSS (Windows Version 13.0; the frontal robe to the cerebellum.