Is toe walking always associated with some neuro or sensory disorder or can it be isolated?
What is the treatment?
Thank you for your help

Toe walking is not specific to any particular disorder or any disorder at all. Many normal children between 1 1/2 - 2 years of age may toe walk intermittently, especially when running. Maybe the relatively flexed hip (as in toddler lordosis and protruding belly) make this a stronger or better balanced position, or maybe locking the ankles lets them use their upper leg strength better, or who knows? Whatever the cause, intermittent, symmetrical toe-walking has no significance.
You need to observe the gait and check the legs for either spacticity (early cp) or weakness and be sure the ankle flexion is normal. Toe walking can also occasionally be related to spinal cord trauma or tethered cord or any other cord malformation, although that may be asymmetric and/or later in presentation.
Nobody has any idea why kids with autism walk on their toes, and it always makes you look twice, but it doen't predict that social interaction problems will appear if they aren't there already. Occasionally autistic kids will stay on their toes so much of the time that their Achilles tendons tighten and they need PT or orthotics to stretch them, but if it's intermittent that is rarely an issue.