MAGNETIC RESONANCE IMAGING CHARACTERISTICS OF PERIPHERAL NERVE SHEATH TUMORS OF THE CANINE BRACHIAL PLEXUS IN 18 DOGS

Magnetic resonance imaging (MRI) examinations from 18 dogs with a histologically confirmed peripheral nerve sheath tumor (PNST) of the brachial plexus were assessed retrospectively. Almost half (8/18) had a diffuse thickening of the brachial plexus nerve(s), six of which extended into the vertebral canal. The other 10/18 dogs had a nodule or mass in the axilla (1.2-338 cm3). Seven of those 10 masses also had diffuse nerve sheath thickening, three of which extended into the vertebral canal. The majority of tumors were hyperintense to muscle on T2-weighted images and isointense on T1-weighted images. Eight of 18 PNSTs had only minimal to mild contrast enhancement and many (13/18) enhanced heterogeneously following gadolinium DTPA administration. Transverse plane images with a large enough field of view (FOV) to include both axillae and the vertebral canal were essential, allowing in-slice comparison to detect lesions by asymmetry of structures. Higher resolution, smaller FOV, multiplanar examination of the cervicothoracic spine was important for appreciating nerve root and foraminal involvement. Short tau inversion recovery, T2-weighted, pre and postcontrast T1-weighted pulse sequences were all useful. Contrast enhancement was critical to detecting subtle diffuse nerve sheath involvement or small isointense nodules, and for accurately identifying the full extent of disease. Some canine brachial plexus tumors can be challenging to detect, requiring a rigorous multiplanar multi-pulse sequence MRI examination.     

POSITIVE CONTRAST MAGNETIC RESONANCE BURSOGRAPHY FOR ASSESSMENT OF THE NAVICULAR BURSA AND SURROUNDING SOFT TISSUES

Magnetic resonance (MR) imaging is often performed to determine the cause of palmar heel pain. We evaluated how distension of the navicular bursa affected the MR appearance of the navicular bursa and associated structures. An MR evaluation was performed on normal cadaver limbs and cadaver limbs from horses with lameness localized to the foot. The normal navicular bursae were injected with 2, 4, or 6 ml of solution. The bursae of the feet from lame horses were injected with 4 or 6 ml, and the MR study was repeated. All bursae were examined grossly to verify the presence or absence of adhesions. Clinical patients that had initial MRI abnormalities suggesting adhesions were also evaluated. Distension of the proximal recess of the normal navicular bursa, proximal to the collateral sesamoidean ligament was achieved with 2 ml. Separation of the collateral sesamoidian ligament from the deep digital flexor tendon (DDFT) was achieved with 4 ml. The separation of the navicular bone from the DDFT and distal sesamoidian impar ligament required 6 ml. Adhesions were more clearly defined in the bursa of the two pathologic cadaver limbs following distension. MR bursography used on clinical patients allowed the determination of the presence or absence of adhesions. In these horses, this determination could not have been definitively made without this technique. MR bursography is useful in horses where the presence of adhesions cannot be clearly defined by MRI.     

FRACTURES OF THE DISTAL PHALANX AND ASSOCIATED SOFT TISSUE AND OSSEOUS ABNORMALITIES IN 22 HORSES WITH OSSIFIED SCLEROTIC UNGUAL CARTILAGES DIAGNOSED WITH MAGNETIC RESONANCE IMAGING

Ungual cartilage ossification in the forelimb is a common finding in horses. Subtle abnormalities associated with the ungual cartilages can be difficult to identify on radiographs. Magnetic resonance (MR) imaging findings of 22 horses (23 forelimbs) with a fracture of the distal phalanx and ossified ungual cartilage were characterized and graded. All horses had a forelimb fracture. Eleven involved a left forelimb (seven medial; four lateral), and 12 involved a right forelimb (five medial; seven lateral). All fractures were nonarticular, simple in configuration, and nondisplaced. The fractures were oriented in an axial proximal to abaxial distal and palmar to dorsal direction, and extended from the base of the ossified ungual cartilage into the distal phalanx. The fracture involved the fossa of the collateral ligament on the distal phalanx in 17 of 23 limbs. The palmar process and ossified ungual cartilage was abnormally mineralized in all horses. Ligaments and soft tissues adjacent to the ossified ungual cartilages were affected in all horses. The routine site of fracture in this study at the base of the ossified ungual cartilage extending into the distal phalanx suggests a biomechanical cause or focal stress point from cycling. The ligamentous structures associated with the ungual cartilages were often affected, showed altered signal intensity as well as enlargement and were thought to be contributing to the lameness. In conclusion, ossified ungual cartilages may lead to fracture of the palmar process of the distal phalanx and injury of the ungual cartilage ligaments.     

CHARACTERISTICS OF CEREBROSPINAL FLUID FLOW IN CAVALIER KING CHARLES SPANIELS ANALYZED USING PHASE VELOCITY CINE MAGNETIC RESONANCE IMAGING

Syringomyelia is an important morbidity source in Cavalier King Charles Spaniels. Although abnormal cerebrospinal fluid (CSF) flow secondary to Chiari malformations is thought to cause syringomyelia in humans, this relationship is unknown in dogs. We used phase-contrast magnetic resonance (MR) imaging to evaluate CSF flow in dogs. Fifty-nine Cavalier King Charles Spaniels were assigned a neurologic grade reflecting their neurologic status. Five normal control dogs of other breeding were imaged for comparison. The presence of syringomyelia was noted from sagittal MR images. The pattern and velocity of CSF flow were assessed using phase-contrast cine MRI at the foramen magnum, C2–C3 disc space, and within syrinxes. Flow was measured most easily with the neck flexed to mimic standing. CSF flow velocity in the dorsal aspect of the subarachnoid space at the foramen magnum was significantly higher in control dogs than Cavalier King Charles Spaniels ( P =0.035). Flow was obstructed at the foramen magnum in 41 of 59 Cavalier King Charles Spaniels. Turbulent flow and jets were associated with syringomyelia presence and severity, and CSF flow velocity at C2/3 dorsally was inversely related to the presence of syringomyelia ( P =0.0197). Peak dorsal subarachnoid space CSF flow velocity at the foramen magnum and C2–C3 were together highly predictive of syringomyelia. CSF flow can be assessed in dogs using phase-contrast cine MRI. Obstruction to flow at the foramen magnum is common in Cavalier King Charles Spaniels and CSF flow pattern and velocity are related to the presence of syringomyelia.     

VALUE OF A SINGLE-SHOT TURBO SPIN-ECHO PULSE SEQUENCE FOR ASSESSING THE ARCHITECTURE OF THE SUBARACHNOID SPACE AND THE CONSTITUTIVE NATURE OF CEREBROSPINAL FLUID

Three case history reports are presented to illustrate the value of the single-shot turbo spin-echo pulse sequence for assessment of the subarachnoid space. The use of the single-shot turbo spin-echo pulse sequence, which is a heavily T2-weighted sequence, allows for a rapid, noninvasive evaluation of the subarachnoid space by using the high signal from cerebrospinal fluid. This sequence can be completed in seconds rather than the several minutes required for a T2-fast spin-echo sequence. Unlike the standard T2-fast spin-echo sequence, a single-shot turbo spin-echo pulse sequence also provides qualitative information about the protein and the cellular content of the cerebrospinal fluid, such as in patients with inflammatory debris or hemorrhage in the cerebrospinal fluid. Although the resolution of the single-shot turbo spin-echo pulse sequence images is relatively poor compared with more conventional sequences, the qualitative information about the subarachnoid space and cerebrospinal fluid and the rapid acquisition time, make it a useful sequence to include in standard protocols of spinal magnetic resonance imaging.     

THE EFFECT OF SEQUENCE SELECTION AND FIELD STRENGTH ON DETECTION OF OSTEOCHONDRAL DEFECTS IN THE METACARPOPHALANGEAL JOINT

Six cadaver forelimbs were imaged in two high‐field magnetic resonance (MR) systems and one low‐field MR system following the creation of osteochondral defects on the palmar distal aspect of the third metacarpal bone. The following sequences were performed using all three systems: proton density (PD) turbo spin echo, T2^* gradient echo (GRE), T2‐weighted fast spin echo, and short tau inversion recovery. In addition, 3D T1 GRE sagittal standard and motion insensitive sequences were obtained using the low‐field system. PD fat saturated and 3D T1‐weighted spoiled GRE images with and without fat suppression were acquired with the high‐field systems. Lesions were measured and assigned a confidence score. The images obtained using high‐field systems (1.0 and 1.5 T) more accurately represented the osteochondral defects when compared with low‐field system (0.27 T) images. The largest difference was observed when evaluating articular cartilage defects, which were not identified on the low‐field images. Sequence selection affected the appearance of the lesions. On all systems the turbo and fast spin echo sequences more accurately represented the lesion size and shape when compared with the GRE sequences. The T1 GRE sequence is the only sequence that appears to allow visualization of the articular cartilage on the low‐field images, but is limited in providing adequate cartilage visualization. Confidence scores were greater on the high‐field systems when compared with the low‐field system.     

Pharmacokinetics of 4-aminopyridine derivatives in dogs

Blockade of potassium channels with 4-aminopryidine (4-AP) restores conduction to demyelinated axons and improves function. Unfortunately, 4-AP causes adverse effects and its clinical effects are unpredictable and limited. Derivatives of 4-AP have been tested in models of spinal cord injury in guinea pigs; three derivatives (methyl-, ethyl- and t -butyl carbamate derivatives) showed promise. This study investigates the safety and pharmacokinetics of these derivatives in dogs. Each derivative was administered orally to dogs starting at doses below effective doses in guinea pigs, and increasing the dose on sequential days. Routine blood work was performed prior to and 24 h after drug administration, blood samples were collected at intervals over 24 h after drug administration, and dogs were monitored for side effects. Derivative plasma levels were determined using high-pressure liquid chromatography. Cerebrospinal fluid (CSF) samples were taken to determine CSF levels. No adverse effects were seen even when using doses higher than those that improved conduction in spinal cord injured guinea pigs. Peak plasma levels occurred at 36.6 (ethyl), 87 ( t -butyl) and 175 (methyl) min and plasma level was related to drug dose. Penetration of the central nervous system (CNS) was good, with CSF levels higher than plasma levels for the t -butyl derivative.     

防治茄二十八星瓢虫Bt菌株的筛选及杀虫活性分析

以从湖北宜昌、襄阳、荆州、广东东莞、安徽安庆5个地区采集得到的52份土样为试材,分别采用温度筛选法、镜检法、PCR-RFLP法和SDS-PAGE等方法,分离了土壤中的苏云金芽孢杆菌,并鉴定了分离出的Bt菌株的基因型,通过茄二十八星瓢虫二龄幼虫的室内杀虫试验测定分离株的杀虫活性,同时分析了部分Bt菌株的伴孢晶体蛋白,以期挖掘新的Bt菌株资源,筛选出对茄二十八星瓢虫具有高毒力的Bt菌株.结果 表明:分离得到10株含cry3基因的菌株,3株含cry7基因的菌株和2株含cry8基因的菌株,得到1株对茄二十八星瓢虫二龄幼虫有高毒力的Bt菌株,当其伴孢晶体悬浮液的浓度在40 mg·mL-1时,校正死亡率最高可达40.42％;发现YC-2-20、GD-4-1均表达分子量约为67 kDa的晶体蛋白;GD-5-7表达分子量约为130 kDa和80 kDa的晶体蛋白;YC-12-6表达分子量约为130 kDa和70 kDa的晶体蛋白.试验筛选出的Bt菌株为农业生产中茄二十八星瓢虫的绿色防控提供了可应用的菌株及基因资源,同时对延缓害虫抗药性的产生也具有重要意义.     

IMAGING DIAGNOSIS—NEURONAL CEROID LIPOFUSCINOSIS WITH A CHRONIC SUBDURAL HEMATOMA

A subdural hematoma was found to accompany neuronal ceroid lipofuscinosis in an 11‐month‐old Dachshund. Results from clinical, magnetic resonance (MR) imaging, histopathologic, ultrastructural, and molecular assessments are described. The dog had a 3‐month history of progressive neurologic signs. In MR images, there was severe asymmetric cerebral atrophy with a subdural hematoma. Histopathologically, there was autofluorescent, periodic acid–Schiff‐positive lipopigment in neurons and transmission electron microscopy confirmed a typical curvilinear profile of the storage bodies. We hypothesize that rapid brain atrophy contributed to the subdural hematoma formation, a complication not described previously in dogs with neuronal lipofuscinosis.     

DEVELOPMENT OF A MORPHOMETRIC MAGNETIC RESONANCE IMAGE PARAMETER SUITABLE FOR DISTINGUISHING BETWEEN NORMAL DOGS AND DOGS WITH CEREBELLAR ATROPHY

Neurodegenerative diseases affect the cerebellum of numerous dog breeds. Although subjective, magnetic resonance (MR) imaging has been used to detect cerebellar atrophy in these diseases, but there are few data available on the normal size range of the cerebellum relative to other brain regions. The purpose of this study was to determine whether the size of the cerebellum maintains a consistent ratio with other brain regions in different ages and breeds of normal dogs and to define a measurement that can be used to identify cerebellar atrophy on MR images. Images from 52 normal and 13 dogs with cerebellar degenerative diseases were obtained. Volume and mid‐sagittal cross‐sectional area of the forebrain, brainstem, and cerebellum were calculated for each normal dog and compared between different breeds and ages as absolute and relative values. The ratio of the cerebellum to total brain and of the brainstem to cerebellum mid‐sagittal cross‐sectional area was compared between normal and affected dogs and the sensitivity and specificity of these ratios at distinguishing normal from affected dogs was calculated. The percentage of the brain occupied by the cerebellum in diverse dog breeds between 1 and 5 years of age was not significantly different, and cerebellar size did not change with increasing age. Using a cut off of 89%, the ratio between the brainstem and cerebellum mid‐sagittal cross‐sectional area could be used successfully to differentiate affected from unaffected dogs with a sensitivity and specificity of 100%, making this ratio an effective tool for identifying cerebellar atrophy on MR images.