**4. Our system proposal**

In order to support and help patients that suffer facial palsy as well as the professionals who treat them, a system to analyze the illness was developed. Our proposal features two modules: WaLi that is an electronic device that it is responsible for data aqcuisition and a graphical user-friendly interface called WaL that displays the processed data.

**WaLi** is a system that features a set of sensors distributed across the face in which are localized the muscles controlled by the seventh nerve. **Figure 1** shows a schematic image that features the seventh cranial nerve following an axial symmetry. At each point shown in **Figure 2(a)**, a set of sensors will be distributed on the same spot to measure each muscle in a differential way.

In order to measure the movement provided by the muscles, eight inertial measurement units that features six freedom degrees were used. The sensors were placed at the frontal, zygomaticus minor, zygomaticus major, risorius, and the pairs by following an axial symmetry. The data generated by the muscles and transmitted to the sensors are sent through several data busses. Although, WaLi (**Figure 3**) is a physical array of electronics devices, it needs software to execute a set of algorithms on the acquired data. The backbone of the software is the acquisition algorithm that is *Medical System to Evaluate the Seventh Cranial Nerve through the Main Facial Mimic Muscles DOI: http://dx.doi.org/10.5772/intechopen.107134*

**Figure 2.**

*Schematic diagram that features hardware system. (a) The circles show the sensor location on the most representative muscles of the facial mimic (frontal, minor zygomatic, risorio, and the major zygomatic) and (b) the data bus that links the sensors to the MCU at the rear.*

**Figure 3.**

*Schematic diagram that shows the sensors distribution across the both hemifaces over the key muscles.*

responsible to gather the data and sending it to the serial port by using a serial communication protocol.

The facial symmetry is the key principle in which the system is based. This is why, the backbone of the entire system focuses on the position at which each sensor is located across the face. In order to keep the position sharp for each sensor, a mask was developed through the fabrication of positive and negative mold. Once the sensors were in place on the key spots, the data busses were positioned in order to not interfere with the facial mimic. Once fixed, the negative mold was used to finish the mask to keep the whole set of arrays in place.

#### **Figure 4.**

*Schematic diagram that shows WaL, the user-friendly interface. In here, it shows the mobility graphs of the frontal muscle in a healthy person. The left side exhibits a set of menus that the user can utilize. The options to manipulate are: (a) patient information; (b) study type; (c) start study; (d) display graphs and hemiface; (e) muscle to show; (f) thresholds and standard deviation; (g) maximum threshold; (h) minimum threshold, (i) mobility degree; (k) and (j) standard deviation of left and right hemiface, respectively.*

**WaL:** It is defined as a user-friendly interface that receives, analyzes, and displays the information obtained from the muscles chosen by the user. **Figure 4** shows a schematic diagram that displays the interface featuring the mobility behavior of a healthy person.

For the development of WaL, a set of algorithms based on numerical analyses were used. The interface established a serial communication between WaLi and WaL in order to collect the data from the serial port. The data are sent through a serial port as a vector. WaL stores and transforms the vector into a matrix. The columns are classified as a function of the hemiface, muscle name, and the plane in which the movement was performed (*x*, *y,* and *z*). Then, the signal is preprocessed to be analyzed later. No human is symmetrical; hereby, at the interface, the user selects the healthy hemiface. The option selected by the user will be considered by the algorithm as a reference. The robustness of the system allows to be used by anyone due to the user-friendly interface.

Another feature that WaL has is the postprocessing feature. A set of statistical analyses can be performed on WaL such as standard deviation, mean, and correlation coefficient. Furthermore, another measurement unit was proposed [64]. The mobility degree (gM) expressed as a percentage of the weakened hemiface as function of the healthy counterpart is obtained by using the following equation:

$$\text{gM} = \frac{\mathbf{100} \times (a\_{2f} - a\_{2i})}{a\_f - a\_i} \tag{1}$$

where *a*2*<sup>i</sup>*: initial component of the weakened hemiface; *a*2*<sup>f</sup>* : final component in *x*, *y* or *z* of the weakened hemiface; *ai*: initial component of the healthy hemiface; *af* : final component of the healthy hemiface.

*Medical System to Evaluate the Seventh Cranial Nerve through the Main Facial Mimic Muscles DOI: http://dx.doi.org/10.5772/intechopen.107134*

Moreover, WaL is capable to analyze and display the state and the information that each sensor has as well as auto-calibration, patient information, and the option to safe the analysis.
