Thirty children with severe, streptococcal-triggered exacerbations of tics or obsessive compulsive disorder (OCD) were treated with plasma exchange (5 in 2 weeks), intravenous immunoglobulin (IVIG, 1 g/kg daily on 2 consecutive days), or placebo saline solution, randomly assigned, in a study at the National Institutes of Health, Bethesda, MD. Neuropsychiatric medications were continued through the study, and oral penicillin or erythromycin was given during follow-up to protect against streptococcal infections. Throat cultures were negative at base-line, and antistreptolysin-0 titers were positive in at least half the patients in each treatment group (mean 350-517). Similar elevations were found for AS deoxyribonucleic B titers. At 1 month, the improvements in the IVIG and plasma exchange groups were 45-58% for OCD, 31-47% for anxiety, 33-35% for overall functioning, and 49% on Tourette syndrome rating scale. The improvements following therapy were maintained at 1 year follow-up, with 14 (82%) of 17 children benefited. 
COMMENT. Immunotherapy with plasma exchange or immunoglobulin are successful in lessening severity of infection-triggered symptoms of obsessive compulsive disorder and Tourette syndrome. These positive results have only been demonstrated in a proportion of children with tics or OCD associated with PANDAS (post-infectious autoimmune neuropsychiatric disorders associated with streptococcal infection). The effects of immunotherapy in patients with chronic symptoms unrelated to PANDAS remains to be determined.
Singer HS in a commentary  notes that immunotherapies are not free of risk, two thirds having side effects. The sustained benefits reported might be explained by spontaneous improvements over time, especially for tics. Furthermore, medications had to be continued in at least half the patients.
An uncontrolled pilot trial in a small group of children with tics associated with ADHD and elevated ASO titers, oral penicillin treatment for 2 to 3 weeks has been associated with a decrease in tics (personal observation). The penicillin administered to all patients in the NIH study may have had a beneficial effect.
Abnormal cortical excitability in OCD and Tourette syndrome. Transcranial magnetic stimulation, previously showing decreased neuronal inhibition in the primary motor area of patients with Tourette syndrome, has demonstrated similar findings in 16 OCD patients in a study at the NIH, Bethesda, MD . The decreases in intracortical inhibition and motor threshold were greatest in OCD patients with comorbid tics.
Suprasellar germinoma presenting with Obsessive-Compulsive symptoms. A 13-year-old boy with a suprasellar germinoma involving the basal ganglia presented with psychotic and obsessive-compulsive symptoms in addition to hemiparesis, diabetes insipidus and impaired academic function . Other neurobehavioral disorders with basal ganglia involvement include Tourette syndrome and PANDAS.