Nuclear medicine of the cerebellum.

Single-photon emission computed tomography (SPECT) and positron emission tomography (PET) with different radiotracers enable regional evaluation of blood flow and glucose metabolism, of receptors and transporters of several molecules, and of abnormal deposition of peptides and proteins in the brain. The cerebellum has been used as a reference region for different radiotracers in several disease conditions. Whole-brain voxel-wise analysis is not affected by a priori knowledge bias and should be preferred. SPECT and PET have contributed to establishing the cerebellum role in motion, cognition, and emotion control in physiologic and pathophysiologic conditions. The basic abnormal imaging findings include decreased or increased uptake of flow or metabolism tracers in the cerebellum alone or as part of a network. Decreased uptake is generally observed in primary structural damage of the cerebellum, but can also represent a distant effect of cerebral damage (crossed diaschisis). Increased uptake can be observed in Freidreich ataxia, inflammatory or immune-mediated diseases of the cerebellum, and in status epilepticus. The possibility is also recognized that primary structural damage of the cerebellum might determine distance effects on other brain structures (reversed diaschisis). So far, SPECT and PET have been predominantly used in clinical studies to investigate cerebellar changes in neurologic and psychiatric diseases and in connection with pharmacologic, transcranial magnetic stimulation, deep-brain stimulation, or surgical treatments.