Magnetic resonance imaging in dogs with neuroangiostrongyliasis (rat lungworm disease).

The magnetic resonance imaging (MRI) appearance of the brain and spinal cord in humans with neuroangiostrongyliasis (NA) due to Angiostrongylus cantonensis infection has been well reported. Equivalent studies in animals are lacking. This case series describes clinical and MRI findings in 11 dogs with presumptively or definitively diagnosed NA. MRI of the brain and/or spinal cord was performed using high-field (1.5 T) or low-field (0.25 T) scanners using various combinations of transverse, sagittal, dorsal and three-dimensional (3D) T1-weighted (T1W), transverse, sagittal and dorsal T2-weighted (T2W), T2W fluid-attenuated inversion recovery (FLAIR) and T2*-weighted (T2*W) gradient echo (GRE), dorsal T2W short tau inversion recovery (STIR) and post-gadolinium transverse, sagittal, dorsal and 3D T1W and transverse T2W FLAIR sequences. In 4/6 cases where the brain was imaged, changes consistent with diffuse meningoencephalitis were observed. Evidence of meningeal involvement was evident even when not clinically apparent. The spinal cord was imaged in 9 dogs, with evidence of meningitis and myelitis detected in regions consistent with the observed neuroanatomical localization. Pathognomonic changes of neural larva migrans, as described in some human patients with NA, were not detected. NA should be considered in the differential diagnosis of dogs with MRI evidence of focal or diffuse meningitis, myelitis and/or encephalitis, especially in areas where A. cantonensis is endemic. If not precluded by imaging findings suggestive of brain herniation, cerebrospinal fluid (CSF) collection for cytology, fluid analysis, real-time polymerase chain reaction (qPCR) and enzyme-linked immunosorbent assay (ELISA) testing should be considered mandatory in such cases after the MRI studies.

Description of technique and lower reference limit for magnetic resonance imaging of hippocampal volumetry in dogs.

OBJECTIVE: To evaluate the use of high-resolution MRI for hippocampal volumetry in dogs and to define a lower reference limit for hippocampal formation (HF) volume. ANIMALS: 20 dogs (with no history of seizures and no underlying structural brain disease) that underwent MRI of the brain. PROCEDURES: The MRI protocol included a high-resolution T1-weighted 3-D ultrafast gradient-echo sequence aligned in a dorsal plane perpendicular to the long axis of the HF. Images obtained with MRI were retrospectively analyzed by 2 observers (A and B). Intraobserver and interobserver agreement were calculated with the Lin concordance correlation coefficient. Volume measurements of the HF were adjusted for intracranial volume, and a lower 95% reference limit for adjusted HF volume was calculated. RESULTS: There was substantial intraobserver agreement (Lin concordance correlation coefficient, 0.97 [95% confidence interval {CI}, 0.94 to 0.99]) but poor interobserver agreement (Lin concordance correlation coefficient, 0.63 [95% CI, 0.37 to 0.79]). The lower 95% reference limit for adjusted HF volume was 0.56 cm(3) (90% CI, 0.52 to 0.60 cm(3)) for the right HF and 0.55 cm(3) (90% CI, 0.52 to 0.58 cm(3)) for the left HF. CONCLUSIONS AND CLINICAL RELEVANCE: HF volumes should be adjusted for intracranial volume to account for the large variation in canine skull size. The amount of time required to perform HF volumetry and low interobserver agreement may restrict this technique to research applications, such as the investigation of epileptic patients for hippocampal sclerosis or other cognitive disorders.