A pinboard by
Michaela Spiteri

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.


Increased pulsatile movement of the hindbrain in syringomyelia associated with the Chiari malformation: cine-MRI with presaturation bolus tracking

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

Chiari-like malformation and syringomyelia in normal cavalier King Charles spaniels: a multiple diagnostic imaging approach.

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

Fractal analysis of MR images in patients with chiari malformation: The importance of preprocessing

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

Delayed retroclival and cervical spinal subdural hematoma complicated by pre-existing Chiari malformation in an adult trauma patient.

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