PhD researcher bridging the gap between machine learning and morphological canine brain MRI analysis
Syringomyelia and Chiari-like Malformation in dogs
Syringomyelia (SM) in dogs is characterised by fluid filled cavities in the spinal cord. Symptoms of SM include an urge to scratch the neck at early stages of the disease, leading to severe pain around the dog's head and neck, causing audible signs of pain. The cavalier King Charles spaniel (CKCS) is also predisposed and associated with the more extreme Chiari-like malformation (CM). Traits that increase risk of SM in the CKCS include bone deformation and displacement in areas surrounding the brain and spinal chord, namely rostral displacement of the atlas and axis, spheno-occipital synchondrosis angulation, reduced occipital crest, increased cervical flexure and odontoid angulation.
To better understand morphological change in SM a novel machine learning approach was developed which removes observer bias. 24 CKCS were grouped into SM absent (16 SMO) and clinical SM (8 SM2), based on clinical history and MRI. CKCS with CM associated pain (SM0) were explicitly excluded. A midline sagittal T2 MRI of the head and neck of a typical CKCS with no SM was chosen as a reference. The remaining 23 MR images were mapped to the reference image using DEMONS (non-linear) image registration, producing a 2D deformation map for each case. Pixel direction and magnitude of the mapping deformation were used as candidate features for automatically identifying SM2 morphology from normal SM0 using a Support Vector Machine classifier. This produced > 95% sensitivity simultaneously with > 92% specificity. The classifier results were mapped back to the reference image, which demonstrated morphological change in the soft palate.
The method can be applied on a variety of different neuro-pathologies and breeds to facilitate diagnosis and understand the location of abnormal morphology. The findings from this study will be used to direct future work in improving the diagnosis and understanding the pathogenesis of the condition.
Abstract: Cine-MRI with presaturation bolus tracking was used in patients with syringomyelia associated with a Chiari malformation to study pulsatile movement of the hindbrain, cervical spinal cord, cerebrospinal fluid and the fluid within the syrinx. Nine patients had 13 examinations, 6 preoperative, 3 after syringosubarachnoid shunting and 4 after posterior fossa decompression. Five controls were also examined. Dynamic display of the acquired images demonstrated downward displacement of the presaturation bolus on the cerebellar tonsils and medulla oblongata (or upper cervical cord) at the C1 level in all preoperative examinations and in two patients after syringo-subarachnoid shunting but with residual foramen magnum obstruction. Downward displacement of the bolus on the cervical spinal cord was also demonstrated in 7 examintions, but not observed in the controls. Thus, the hind-brain-spinal cord axis showed larger pulsatile movements in patients with foramen magnum obstruction. Based on these observations and a review of the literature, a new theory on the mode of extension of syringomyelia, emphasising the role of increased pulsatile movement of the hind-brain-spinal cord axis is proposed: that the pulsatile movements, together with a one-way valve mechanism in the syrinx cavity act as a “vacuum-pump” to enlarge the syrinx.
Pub.: 01 Feb '94, Pinned: 30 Jun '17
Abstract: The objectives of the study were (1) to report the incidence of Chiari-like malformation and syringomyelia in a normal French cavalier King Charles spaniel breeding population; (2) to precise the standard computed tomography dimensions of the caudal fossa and (3) to investigate the use of ultrasonography in diagnosis of this syndrome.Clinically normal adult cavalier King Charles spaniel underwent ultrasonographic examination of the spinal cord and caudal fossa. Computed tomography was used to measure the caudal fossa and magnetic resonance imaging allowed syringomyelia and cerebellar herniation identification.Of the 16 dogs in the study, seven had syringomyelia (43.7 per cent). All dogs had cerebellar herniation, suggesting Chiari-like malformation and also a tendency to occipital dysplasia. Computed tomography measurements of the caudal fossa are reported. In one dog, a syrinx was identified by ultrasonography. The only difference between dogs with or without syringomyelia was that dogs with Chiari-like malformation/syringomyelia were statistically older.The incidence of Chiari-like malformation and syringomyelia may be high in an asymptomatic population of cavalier King Charles spaniel . Computed tomography measurements reported in this study should now be compared with those of a symptomatic population to evaluate the hypothesis that dogs with Chiari-like malformation/syringomyelia syndrome have a smaller caudal fossa. This study did not identify a smaller caudal fossa in an asymptomatic cavalier King Charles spaniel population with syringomyelia. Ultrasonography probably has a low sensitivity for diagnosis of Chiari-like malformation/syringomyelia.
Pub.: 18 Jul '08, Pinned: 30 Jun '17
Abstract: This study describes Chiari-like malformation and syringomyelia in the Griffon Bruxellois and establishes if skull radiographs are useful for disease prediction.Magnetic resonance imaging from 56 Griffon Bruxellois dogs was assessed for Chiari-like malformation and cerebrospinal fluid pathway abnormalities. Skull radiographs were obtained in 33 dogs. Two rostrocaudal and two ventrodorsal measurements were made, and ratios of one length to another were compared.In this selected sample, 60.7 per cent had Chiari-like malformation. Syringomyelia occurred with and without Chiari-like malformation (37.5 and 8.9 per cent study population, respectively). The radiographic study demonstrated that one measurement ratio could be used to predict Chiari-like malformation (sensitivity of 87 per cent and specificity of 78 per cent) and that there were significant interaction factors between sex and syringomyelia for two measurement ratios.The study suggests that Chiari-like malformation is characterised by a shortening of the basicranium and supra-occipital bone with a compensatory lengthening of the cranial vault, especially the parietal bone. We described a simple radiographic technique, which may be useful as a screening test until a more definite genetic test for Chiari-like malformation is available.
Pub.: 20 Aug '09, Pinned: 30 Jun '17
Abstract: We report a 36 year-old woman who presented with headaches and hypoesthesia of the face. MRI revealed a large dumbbell shaped trigeminal neurinoma extending into both the middle and the posterior cranial fossae. In addition, there was a Chiari I malformation and syringomyelia. Within two months of tumor resection, both the Chiari malformation and the syringomyelia resolved. The association of an intracranial space-occupying lesion with Chiari malformation and syringomyelia is reviewed.
Pub.: 05 Jul '05, Pinned: 30 Jun '17
Abstract: This study aimed to develop a system of quantitative analysis of canine Chiari-like malformation and syringomyelia on variable quality MRI. We made a series of measurements from magnetic resonance DICOM images from Griffon Bruxellois dogs with and without Chiari-like malformation and syringomyelia and identified several significant variables. We found that in the Griffon Bruxellois dog, Chiari-like malformation is characterized by an apparent shortening of the entire cranial base and possibly by increased proximity of the atlas to the occiput. As a compensatory change, there appears to be an increased height of the rostral cranial cavity with lengthening of the dorsal cranial vault and considerable reorganization of the brain parenchyma including ventral deviation of the olfactory bulbs and rostral invagination of the cerebellum under the occipital lobes.
Pub.: 18 Feb '14, Pinned: 30 Jun '17
Abstract: Chiari Malformation type I (CM-I) is a serious neurological disorder that is characterized by hindbrain herniation. Our aim was to evaluate the usefulness of fractal analysis in CM-I patients. To examine the morphological complexity features of this disorder, fractal dimension (FD) of cerebellar regions were estimated from magnetic resonance images (MRI) of 17 patients with CM-I and 16 healthy control subjects in this study. The areas of white matter (WM), gray matter (GM) and cerebrospinal fluid (CSF) were calculated and the corresponding FD values were computed using a 2D box-counting method in both groups. The results indicated that CM-I patients had significantly higher (p<0.05) FD values of GM, WM and CSF tissues compared to control group. According to the results of correlation analysis between FD values and the corresponding area values, FD and area values of GM tissues in the patients group were found to be correlated. The results of the present study suggest that FD values of cerebellar regions may be a discriminative feature and a useful marker for investigation of abnormalities in the cerebellum of CM-I patients. Further studies to explore the changes in cerebellar regions with the help of 3D FD analysis and volumetric calculations should be performed as a future work.
Pub.: 21 Jul '15, Pinned: 30 Jun '17
Abstract: Voxel-based morphometry (VBM) enables an unbiased in-vivo whole-brain quantitative analysis of differences in gray matter (GM), white matter (WM) and cerebro-spinal fluid (CSF) volumes. We assessed with VBM 20 spinocerebellar ataxia Type 2 (SCA2) patients with mild or moderate cerebellar deficit and 20 age and sex-matched healthy controls. SCA2 patients showed a significant (P < 0.05 corrected for multiple comparison) symmetric loss of GM in the cerebellar vermis and hemispheres sparing lobules I,II, Crus II,VII, and X, and of the WM in the peridentate region, middle cerebellar peduncles, dorsal pons, and cerebral peduncles. The CSF volume was increased in the posterior cranial fossa. No GM, WM or CSF volume changes were observed in the supratentorial compartment. A mild (P < 0.05, >0.01) correlation was observed between the GM and WM loss and severity of the neurological deficit. In SCA2 patients with mild to moderate cerebellar deficit, GM and WM volume loss and CSF volume increase are confined to the posterior cranial fossa.
Pub.: 04 Mar '08, Pinned: 30 Jun '17
Abstract: As a popular method to meathe complexity of images and generally signals, FD analyses have been used in neuroimaging studies to evaluate the morphological complexity of brain structures. The aim of this study is to perform an FD-based complexity analyses of cerebellar tissues, such as cerebellar white matter (WM), cerebellar gray matter (GM) and cerebrospinal fluid (CSF) spaces around the cerebellum, on magnetic resonance (MR) images of Chiari Malformation type-I (CM-I) patients and healthy controls. Besides, to determine the noise effects on complexity of sub cerebellar structures, two common non-linear noise filters, median filter and bilateral filter, were applied to MR images and their performances were compared. Data of fourteen CM-I patients and sixteen normal subjects were used in this study. First, noise variance was estimated using a method based on skewness of the magnitude data. Second, as a preprocessing step, median and bilateral filters were applied on MR data separately to create different series of images for each filter. After the preprocessing, filtered brain images were segmented into three different tissues including WM, GM and CSF. Last, a 3D box-counting method was applied on segmented images to estimate the corresponding FD values. Our results showed that, while GM FD values was not significantly different between patients and controls (p = 0.051) in median filtering case, GM FD values in patients were found to be significantly lower than those in controls (p = 0.007) in bilateral filtering case. Additionally, in both cases, WM FD values in patients were found to be significantly lower than those in controls; however, this difference was more evident in bilateral filtering case (p = 0.0003) than that in median filtering case (p = 0.013). These outcomes indicated that bilateral filter was found to be more successful in discriminating CM-I patients from controls in cerebellar complexity analyses. In conclusion, results of this study revealed that noise removal is an important preprocessing step for a more successful analysis of digital images and bilateral filter is an effective filtering method for segmentation accuracy and FD analysis performance.
Pub.: 21 Jul '16, Pinned: 30 Jun '17
Abstract: Chiari malformation type I (CM-I), described by a descent of the cerebellar tonsils, is assumed to be a neurological developmental disorder. The aim of the present study was to investigate morphological variance in cerebellar sub-structures, including gray matter (GM), white matter (WM), and cerebrospinal fluid (CSF), using magnetic resonance (MR) images with three-dimensional (3D) fractal dimension (FD) analysis in patients with CM-I. MRI data of 16 patients and 15 control subjects were obtained, and structural complexity analyses were performed using a box-counting FD algorithm. Results showed that patients with CM-I had significantly reduced FD values for WM and CSF in comparison with controls, and statistically significant differences in cerebellar GM and CSF volumes between patients and controls were found. Moreover, a significant difference was not found between the WM volumes. This may suggest that there are changes in structural complexity in WM even when its volume is unaffected. We conclude that the findings of this preliminary study indicate the possibility of using FD analysis to understand the pathophysiology of CM-I in patients.
Pub.: 08 Jun '17, Pinned: 30 Jun '17
Abstract: Hurler Syndrome is the most severe phenotype of mucopolysaccharidosis type I. With bone marrow transplant and enzyme replacement therapy, the life expectancy of a child with Hurler syndrome has been extended, predisposing them to multiple musculoskeletal issues most commonly involving the spine.This is the case report of a 6-year-old male with Hurler syndrome who was diagnosed with Chiari I malformation and cervicothoracic syringomyelia on a preoperative magnetic resonance imaging (MRI) for his thoracolumbar kyphosis. This report details the successful management of a Chiari I malformation and syringomyelia with posterior fossa decompression in a child with Hurler syndrome.Children born with MPS I can have complex spine issues that require surgical management. The most common orthopedic spinal condition for these patients, thoracolumbar kyphosis, requires evaluation with an MRI before performing surgery. This resulted in the diagnosis of a Chiari I malformation and syringomyelia in our patient with Hurler syndrome. This was successfully treated with decompression of the posterior fossa.
Pub.: 14 Jun '17, Pinned: 30 Jun '17
Abstract: Traumatic spinal subdural hematoma involving the retroclival region and upper cervical spine is a rare pathology. To our knowledge, there have only been two prior cases in an adult trauma patient. We describe a patient with pre-existing Chiari 1 malformation, who recently sustained a unilateral Type 1 OCF (occipital condyle fracture) with associated disruption of the tectorial membrane and transverse ligament, that returned with a retroclival subdural hematoma extending down to C7, causing spinal cord compression and symptomatic obstructive hydrocephalus.A 30-year-old female sustained a motor vehicle collision. CT C spine revealed a Type I OCF. MRI C spine demonstrated disruption of the tectorial membrane and avulsion of the transverse ligament at its attachment to the left C1 tubercle; moreover, there was a Chiari 1 malformation. Patient was neurologically intact. A halo was recommended but patient opted for an aspen collar with close management. Patient was discharged, but returned 3 days later with apneic episodes, along with bradycardia and hypertension. She was promptly intubated. CT head showed interval ventricular enlargement. MRI C spine revealed a new ventral hematoma spanning the retroclival region to C7, most pronounced at C2-C3. On exam, she opened her eyes to pain, pupils equal and reactive, and she withdrew in all extremities. An external ventricular drain (EVD) was emergently placed. She underwent a sub-occipital craniectomy, C1-3 laminectomies, and occiput-C4 instrumented fusion. The dura was significantly tense, and no epidural hematoma was observed during lateral exploration. Postoperatively, she woke up well, exhibiting a non-focal neurological exam. A diagnostic angiogram was negative. She was extubated uneventfully, and the EVD was weaned off in four days.Traumatic spinal subdural hematoma involving both the retroclival region and upper cervical spine can lead to bulbar signs and symptomatic obstructive hydrocephalus. There should be vigilance for this pathology in patients with high energy cranio-cervical trauma. Disruption of the tectorial membrane and therapeutic anticoagulation may be risk factors. The clinical scenario can be complicated in the setting of a pre-existing Chiari 1 malformation.
Pub.: 26 Jun '17, Pinned: 30 Jun '17