# Portable RGB-D Camera-Based System for Assessing Gait Impairment Progression in ATTRv Amyloidosis
## 2 Materials and Methods  
### Subjects  
We carried out an experiment at LABIOMEP (Porto Biomechanics Laboratory) where data were acquired once (T0) and then a year and a half later (T1) from 6 ATTRV amyloidosis patients (4 male and 2 female). The experiment was approved by the Ethics Committee of the Hospital Santo Antonio (Centro Hospitalar Universitario do Porto, Porto, Portugal) and complied with the Declaration of Helsinki. All patients provided their written informed consent. The patients were being followed at Unidade Corino de Andrade (Centro Hospitalar Universitario do Porto) in an external consultation. Their demographic data, as well as clinical condition and progression information, are presented in Table 1. The only exclusion criterion was the presence of comorbidities. All participants were patients with the V30M mutation, but with different gait impairment degrees. They all had pain, thermal and tactile anesthesia, as well as reduced proprioception. They also presented some degree of motor deficit at the lower limbs. One patient had no strength deficit but had difficulty walking on heels, while the others lacked dorsiflexion from 4/5 to 0/5 (Medical Research Council Scale [54]) and plantar flexion from 4/5 to 1/5. All patients had a normal knee segmental force (5/5) at both T0 and T1. Overall, patients presented sensory ataxia and steppage gait with different instability and movement coordination degrees during stride. Steppage gait is characterized by the loss of dorsiflexion, consequent foot drop and high lifting of the leg. Visually, patients spread the legs to improve balance, exaggerate knee and hip flexion and are often observed \"throwing\" the feet forward, thereby improving ground clearance. They presented, therefore, very heterogeneous gait, although the clinical perception is that all alterations resulted from the sensory-motor polyneuropathy caused by the disease. The clinical evolution observed in each patient between T0 and T1 is described in Table 2.  
Regarding treatment, three patients had been taking medication (tafamidis) for 10 months (P3), 3 years (P2), and 6 years (P1). One patient was enrolled in a different clinical trial for \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Patient** & **Clinical Condition at T0** & **Clinical Condition at T1** & **PND Score** & **TTR-FAP Score** \\ \hline
**P1** & Dorsiflexion deficit (4) & Dorsiflexion deficit (4\(-\)) & II & I \\
**P2** & Dorsiflexion (0), plantar flexion (1), & Dorsiflexion (0), plantar flexion (0), knee flexion (4\(-\)), high steppage & II & I \\
**P3** & Difficulty walking on heels only & Difficulty walking on heels only \& weakness at the toes & I & I \\
**P4** & Dorsiflexion (0), plantar flexion (3), steppage & Dorsiflexion (3), plantar flexion (4), very low steppage & II & I \\
**P5** & Dorsiflexion (4), plantar flexion (4), & Dorsiflexion (3), plantar flexion (4), steppage & II & I \\
**P6** & Dorsiflexion (2), plantar flexion (1), steppage & Dorsiflexion (1), steppage & II & I \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Clinical evolution of the ATTRV amyloidosis patients evaluated based on the Medical Research Council (MRC) Scale (0 is the worst condition and 5 the best). The PND (Polyneuropathy Disability) and ATTRV amyloidosis scores are also indicated (the values were the same at T0 and T1). PND score (0: no impairment, I: sensory disturbances but preserved walking capability, II: impaired walking capability but ability to walk without a stick or crutches, III a: walking only with the help of one stick or crutch, III b: walking with the help of two sticks or crutches, IV: confined to a wheelchair or bedridden); TTR-FAP score (I—sensory polyneuropathy, II—progressive walking disability, and III—wheelchair-bound or bedridden).