The paravertebral ganglia are connected via spinal nerves
inwhich region?

Answer is thoracic region.

Explanation:

Paravertebral ganglia are subdivision of peripheral sympathetic nervous system , which is one of the part of autonomic nervous system found in mammals. Its components are superior and inferior mesenteric ganglia and celiac.

The spinal nerves are peripheral nerves arising from the spinal cord. These spinal nerves are altogether 31 pairs. 8 in cervical, 12 in thoracic, 5 lumbar, 5 in sacral, and 1 in caudal.

There are two types of spinal nerves composed of the sensory and motor fibres.