We are given that ${a_n}$ is an arithmetic sequence with first term $a_1=8$ and the sum of its fourth and sixth terms is zero, i.e., $a_4+a_6=0$. We need to find the sum of the first 8 terms, denoted by $S_8$.

First, let's write down the given information in mathematical notation:
$$\begin{cases} a_1 = 8, \\ a_4 + a_6 = 0. \end{cases}$$

Since ${a_n}$ is an arithmetic sequence, we can express $a_4$ and $a_6$ in terms of $a_1$ and the common difference $d$:
$$\begin{cases} a_1 = 8, \\ a_1 + 3d + a_1 + 5d = 0. \end{cases}$$

Now, we can solve this system of linear equations to find the values of $a_1$ and $d$. Substituting $a_1=8$ into the second equation, we get:
$$\begin{cases} a_1 = 8, \\ 8 + 3d + 8 + 5d = 0. \end{cases}$$

Simplifying the second equation, we obtain:
$$\begin{cases} a_1 = 8, \\ 8d = -16. \end{cases}$$

Dividing both sides of the second equation by $8$, we find:
$$\begin{cases} a_1 = 8, \\ d = -2. \end{cases}$$

Now that we have found the values of $a_1$ and $d$, we can calculate $S_8$ using the formula for the sum of an arithmetic series:
$$S_n = \frac{n}{2}[2a_1 + (n - 1)d].$$

Substituting the values we found, we have:
$$S_8 = \frac{8}{2}[2 \cdot 8 + (8 - 1) \cdot (-2)].$$

Simplifying the expression inside the brackets, we get:
$$S_8 = 4[16 - 14].$$

Finally, computing the value of $S_8$, we obtain:
$$S_8 = 4[2] = \boxed{8}.$$