The Sensory Field and Repeatability of the Cutaneous Trunci Muscle Reflex of the Dog

Abstract

Objective To describe the cutaneous trunci muscle (CTM) reflex in dogs. Study Design Prospective descriptive study. Animals Normal dogs (n = 155) and 10 dogs with thoracolumbar myelopathies. Methods The CTM reflex caudal border was assessed from the ilial crests moving cranially until a CTM contraction was elicited. The lateral borders were evaluated at 4 levels and the distance from the midline to the lateral border was expressed as a percentage of the trunk hemicircumference. The caudal border was assessed in 10 dogs with myelopathies by 4 different observers and by 1 observer on 3 occasions; the inter- and intraobserver kappa coefficient was calculated. Results The CTM reflex was elicited in all dogs. Its caudal border was at L5 or L6 in 153 dogs and at L1 and L3 in 2 dogs. The lateral field of the reflex occupied >50% of the hemicircumference of the trunk at each level tested. The mean difference in measurement of the reflex caudal border was 0.55 cm between observers and 0.28 cm for the same observer. The inter- and intraobserver kappa coefficient was 0.67 and 0.87, respectively. Conclusions The CTM reflex is elicited caudal to L5 in most normal dogs, and the lateral sensory field extends to 50% or more of the circumference of the trunk. Inter- and intraobserver differences in assessment of the caudal border are low.

Acute Spinal Cord Injury

“…The cutaneous trunci muscle reflex in normal dogs is present as far caudally as the skin overlying L5 or L6 vertebrae, as recently described in 153 of 155 normal dogs. 31 The recommendation in cases with trauma to the vertebral column is to image the entire spine to search for multiple lesions, all of which might not be clinically detectable. Five percent to 10% of cases with trauma to the vertebral column have multiple fractures or luxations.…”

The Cutaneous Trunci Muscle Reflex: A Predictor of Recovery in Dogs with Acute Thoracolumbar Myelopathies Caused by Intervertebral Disc Extrusions

“…The sensory stimulus induces a contraction of the CTM, producing a skin twitch. The caudal border of the CTM reflex lies at the level of the 6th lumbar vertebra (L6) in 97% of normal dogs . Thoracolumbar myelopathies affecting spinal cord segments T3 – L3 interrupt the ascending CTM reflex pathway, causing cranial movement of the caudal border, and this change in level of border is commonly used to localize spinal cord lesions.…”

The cutaneous trunci reflex for localising and grading thoracolumbar spinal cord injuries in dogs

“…The literature suggests that the cutaneous trunci reflex may be absent in some healthy dogs and this could represent a limitation for using it clinically (De Lahunta and Glass ). However, studies in dogs concluded that the cutaneous trunci reflex could be reliably demonstrated in the vast majority (94 to 100%) of healthy dogs up to the vertebral level L6 (Fox , Muguet‐Chanoit and others , Muguet‐Chanoit and others ). The cutaneous trunci reflex was present in all dogs in this study, either cranial to the level of cut‐off or cranial to L6 in cases with no cut‐off.…”

“…The cutaneous trunci reflex is a polysynaptic reflex with intersegmental transmission of impulses. It is elicited by pinching the skin of the dorsal trunk between the second thoracic vertebra (T2) and the sixth to seventh lumbar vertebrae (L6 or L7) and observing a contraction of the cutaneous trunci muscles bilaterally (Holstege and others , Blight and others , Garosi , Muguet‐Chanoit and others ). Within the spinal cord segment corresponding to a particular dermatome, the sensory neurons synapse on long interneurons at the level of the dorsal grey column and the axons of these long interneurons enter the fasciculus proprius of the spinal cord bilaterally.…”

“…The presence of a cutaneous trunci reflex cut‐off can be used as an aid to localising lesions affecting the thoracolumbar spinal cord (Fox , Borgens and others ), but the accuracy of the cutaneous trunci reflex cut‐off in predicting lesion localisation has not been assessed. It has been suggested that the cutaneous trunci reflex may be absent in healthy dogs (De Lahunta and Glass ); however, studies have shown that the reflex may be reliably demonstrated in most, if not all, healthy dogs up to the vertebral level L6 (Fox , Muguet‐Chanoit and others , Muguet‐Chanoit and others ) and the reflex is consistently affected in dogs with injuries cranial to L1 (Olby and others ).…”