Cerebrospinal fluid flow in small-breed dogs with idiopathic epilepsy observed using time-spatial labeling inversion pulse images: a preliminary study

Abstract

Cerebrospinal fluid (CSF) circulation diseases, such as hydrocephalus and syringomyelia, are common in small-breed dogs. In human patients with CSF circulation diseases, time-spatial labeling inversion pulse (time-SLIP) sequence performed to evaluate CSF flow before and after treatment allows visualization of the restoration of CSF movement. However, studies evaluating CSF flow using the time-SLIP method in small-breed dogs are limited. Therefore, the present study aimed to evaluate intracranial CSF flow on time-SLIP images in small-breed dogs with idiopathic epilepsy, as an alternative model to healthy dogs. Time-SLIP images were obtained at two sites: 1) the mesencephalic aqueduct (MA) area (third ventricle, MA, and brain-base subarachnoid space [SAS]) and 2) the craniocervical junction area (fourth ventricle, brainstem, and cervical spinal cord SAS) to allow subsequent evaluation of the rostral and caudal CSF flow using subjective and objective methods. In total, six dogs were included. Caudal flow at the MA and brain-base SAS and rostral flow in the brainstem SAS were subjectively and objectively observed in all and 5/6 dogs, respectively. Objective evaluation revealed that a significantly smaller movement of the CSF, assessed as the absence of CSF flow by subjective evaluation, could be detected in some areas. In small-breed dogs, the MA, brain-base, and brainstem SAS would be appropriate areas for evaluating CSF movement, either in the rostral or caudal flows on time-SLIP images. In areas where CSF movement cannot detected by subjective methods, an objective evaluation should be conducted.

Keywords: canine; cerebrospinal fluid; magnetic resonance imaging; syringomyelia; time-spatial labeling inversion pulse.

Fig. 1.

Mid-sagittal T2-weighted (A, C) and time-spatial labeling inversion pulse (B, D) images of a 4.3-kg, 7-year-old, Japanese Terrier dog. (A) The mesencephalic aqueduct (MA) time-spatial labeling inversion pulse (time-SLIP) image was set based on mid-sagittal T2-weighted image (A). The plane of the MA time-SLIP image was put in the same location as (A) the mid-sagittal plane. The tagged area (tag) on the MA time-SLIP image (the area surrounded by the yellow open box) was set on the plane perpendicular to the sagittal plane (the point where the caudal edge of tag overlapped the rostral part of MA), at an angle perpendicular to MA (red dotted line). (B) Actual time-SLIP image. On the image, signals outside the tag were suppressed by non-selective inversion pulse (black). Inversely, signals of cerebrospinal fluid (CSF) inside the tag were restored by selective inversion pulse, and were consequently shown as hyperintensity (white). (C) The craniocervical junction (CCJ) time-SLIP image was also set based on mid-sagittal T2-weighted image (C). The plane of the CCJ time-SLIP image was placed in the same location as (C), in the mid-sagittal plane. The tag on the CCJ time-SLIP image (the area surrounded by the green open box) was set at the plane perpendicular to the sagittal plane, the point where the caudal edge of the tag contacted with the most caudal part of the cerebellum, and an angle perpendicular to the red line, the point (closed red circle, a) where the rostral edge of the tag intersects the dorsal edge of the medulla oblongata, and connects with the point (open red circle, b) where the caudal edge of the tag intersects the dorsal edge of the medulla oblongata at the level of the most caudal part of the cerebellum. (D) Actual time-SLIP image. Only CSF signals inside the tag are shown as hyperintensity.

Fig. 2.

(A) Schema for the mid-sagittal image of the same dog as shown Fig. 1. Location of the tagged area (tag) on the mesencephalic aqueduct (MA) time-spatial labeling inversion pulse (time-SLIP) image is presented. Blue and red lines indicate the rostral and caudal edge of the tag, respectively; as such, the tag is the area between the blue and red lines. (B) Enlargement of the area surrounded by the green box in (A). Roman numbers indicate each observation point of cerebrospinal fluid (CSF) flow. At each observation point, the presence of rostral and caudal flows was evaluated. White arrows indicate CSF flowing out of the tag (flow-out), while black arrows indicate CSF flowing into the tag (flow-in). (C) The anatomical locations of each observation point on the MA time-SLIP image are presented. (D) Schema for the mid-sagittal image of the same dog as in Fig. 1. Location of tag on the craniocervical junction (CCJ) time-SLIP image is shown. The tag is shown using the same-colored lines as (A). (E) Enlargement of the area surrounded by the yellow green box in (D). Roman numbers indicate each observation point of the CSF flow. White and black arrows indicate the flow-out or flow-in, respectively, as in (B). (F) Anatomical locations of each observation point on CCJ time-SLIP image are presented. *SAS: subarachnoid space.

Fig. 3.

Sequential series of the mesencephalic aqueduct (A–C) and the craniocervical junction (D–F) time-spatial inversion pulse images of a 2.8-kg, 9-year-old Yorkshire Terrier dog. On each panel, blue and red lines indicate the rostral and caudal edges of the tagged area (tag). (A) Roman numbers indicate the observation points of cerebrospinal fluid (CSF) flow on the mesencephalic aqueduct (MA) time-spatial labeling inversion pulse (time-SLIP) images [I: third ventricle, II: subarachnoid space (SAS) ventral to the frontal lobe of the cerebrum, III: MA, IV: ventral brainstem SAS]. The CSF inside the tag is shown as hyperintensity (white), while those outside the tag (non-tagged area) are shown as hypointense (black). (B, C) CSF outside the tag (indicated by white arrows) is shown as white, compared to A, which indicates that the tagged CSF flows out of the tag during inversion time (TI) (flow-out). The CSF inside the tag (indicated by black arrows) is shown in black compared to A, indicating that non-tagged CSF flows into the tag during TI (flow-in). The signals of the CSF in the remaining observation points do not change compared to A, indicating that the CSF in these areas does not flow during TI. (D) Roman numbers indicate the observation points of CSF flow on the craniocervical junction time-SLIP images [V: fourth ventricle, VI: ventral brainstem SAS, VII: dorsal cervical SAS, VIII: ventral cervical SAS]. (E, F) White or black arrows indicate flow-out or flow-in CSF flow, as (B, C), respectively.

Fig. 4.

Mean (A), maximum (B), and minimum (C) flow distance of cerebrospinal fluid on time-spatial labeling inversion pulse images. The mean and maximum flow distances were significantly greater in the SP/OP group than those in the SA/OP group. The maximum flow distance was significantly greater in the Sa/OP group than that in the SA/OP group. The flow was subjectively assessed as absent due to agreement of the evaluations among reviewers, while flow was objectively assessed as present in the SA/OP group; the flow was subjectively assessed as absent due to disagreement of evaluations among reviewers, while flow was objectively assessed as present in the Sa/OP group; and the flow was subjectively and objectively assessed as present in the SP/OP group. *: P<0.05, **: P<0.01.