question about isotropic subspaces

Question

if $V$ is a complex vector space of dimension $2n$ and $Q$ a bilinear form over $V$, the definition of an isotropic subspace is the following: $$\Lambda:Q(\Lambda,\Lambda) \equiv 0$$.
Suppose that $\Lambda$ is a moaximal isotropic subspae, i.e. it isn't contained in any isotropic supspace.
So i see that the dimension of any isotropic subspace is lower than $dim(V)/2$. Furthermore all maximal isotropic subspace must have the same dimension.
Are there some conditions such that all isotropic subspace must have dimension $n$? i think that in general this doesn't happen.