3D didactic model and useful guide of the semicircular conducts

Knowledge of the anatomy and physiology of the semicircular canals and their central pathways is essential for the diagnosis of vestibular pathology. This 3 dimensional (3D) scheme of the Semicircular Canals (SSCC) is a teaching tool and a useful reference guide for rapid consultation. Material and methods A multicolored cardboard model is accompanied by a user manual which provides a thorough description of the tool for the most common vestibular diseases. Results Although results cannot be quantitatively assessed, the model has been well received at several Latin American scientific conferences. The model is often understood with verbal instruction only; nevertheless, a printed user manual is included. Conclusions This 3 dimensional (3D) model of the Semicircular Canals (SSCC) is a practical, low cost tool for use in private and academic settings.


INTRODUCTION
The management of vestibular pathology, peripheral or central, requires prior knowledge of the anatomy and physiology 1,2,3,4,5,6 of the semicircular canals 2,3,5 and their central pathways 7. The anatomy and pathology of the semicircular canals are particularly difficult to interpret due to the complex geometry and physiological variations between the horizontal and the vertical semicircular canals.
This 3D model of the Semicircular Canals (SSCC) is intended for use as a didactic tool and a quick reference guide when dealing with various pathologies of the labyrinth. It is especially effective in the diagnosis and possible treatment of Benign Paroxysmal Positional Vertigo (BPPV) 8,9,10,11 , as well as the interpretation of the causes of Vestibular Hypofunction 12 , per the Head Thrust Test 7,9 and in the identification of different Neuritis (inflammatory neuropathies), Canal Fistulas 9 and Vascular Disorders, based on a knowledge of physiology, innervation and vascular supply of the SSCC 4. It also describes Downbeat and Upbeat Nystagmus (Pitch) and Torsional Nystagmus (Roll) 7 as a part of the Central Vestibular Pathway in a simple and practical way. It is not intended for use as an anatomically correct model, but as a rough spatial reference. The model does not intend to explain the clinical examination nor pathology in detail, however, and requires some baseline knowledge of the vestibular system for a more complete understanding.
It is not intended to replace more complete reference books in this area. The model (SSCC3D) is portable and easy to use.

MATERIAL AND METHODS
The multicolored cardboard model (Table 1)

RESULTS
This 3D Model is the result of amalgamation of the anatomy and physiology of the semicircular canals. In the  Each one of the faces of the SSCC has the following information as displayed in Fig.3, in which the Right Posterior Semicircular Canal (RPSC) is shown as an example, since it is in this conduct where BPPV can often be found. Each one face presents the same information in the same 16 -The thick arrow shows that the excitatory stimulation is stronger than inhibition. 17 -The thin arrow shows the inhibitory stimulus. The inhibitory stimulus is ampullipetal. 18 -Each semicircular canal is color coded, and those which share the same color work together when stimulated. 19 -Slow phases. 20 -The round headed indicates that movement of the eye, and they are placed to remember that during the Ny, the rotatory motion is clearer seen when the patient look outward, and vertical motion when he look inward. location. The faces of the horizontal canals are arranged differently, however, with the same concept. A partial diagram of the central symbology is displayed in Fig.4; however it is explained in greater detail in the users guide that accompanies the model. In the inferior faces of the horizontal SSCC there is a diagram of the most frequent vascular supplies to the inner ear, its innervation and vascular variations.
Following a color code, the arteries are in red, the veins in dark blue, and the venous drainage of the corresponding vein in light blue. The nerves are in green. Fig.5. In the posterior face of the SSCC there is a diagram that shows the distribution and relation of the different nerves that pass by the internal auditory canal (posterior sight) Fig. 6. The model has been very well received at various Latin American scientific conferences as listed below.

DISCUSSION
This 3D model is a useful tool to teach concepts of anatomy, physiology and pathology without the need of texts. It is a practical, low cost tool for use in private and academic settings.
This essay has been abridged and we advise reading the complete user manual for a more complete understanding of this tool.