Tourette syndrome (TS) is a childhood neuropsychiatric disorder characterized by motor and vocal tics. Imaging studies found alterations in caudate (Cd) and putamen volumes. To investigate possible alterations in cell populations, postmortem basal ganglia tissue from individuals with TS and normal controls was analyzed by using unbiased stereological techniques. A markedly higher total neuron number was found in the globus pallidus pars interna (GPi) of TS. In contrast, a lower neuron number and density was observed in the globus pallidus pars externa and in the Cd. An increased number and proportion of the GPi neurons were positive for the calcium-binding protein parvalbumin in tissue from TS subjects, whereas lower densities of parvalbumin-positive interneurons were observed in both the Cd and putamen of TS subjects. This change is consistent with a developmental defect in tangential migration of some GABAergic neurons. The imbalance in striatal and GPi inhibitory neuron distribution suggests that the functional dynamics of cortico-striato-thalamic circuitry are fundamentally altered in severe, persistent TS.T ourette syndrome (TS) is a childhood neuropsychiatric disorder characterized by persistent motor and vocal tics, which may or may not abate upon entering adulthood. Tics are sudden stereotyped motor sequences of varying intensity and complexity, often preceded by compulsions or sensory phenomena. Neither the etiology nor the pathophysiology of TS is well understood. Both genetic and environmental factors are thought to be important, but the exact role of each has not yet been identified (1). Epigenetic events that increase the risk of developing tic disorder or TS include perinatal hypoxic-ischemic events that damage the periventricular germinal matrix and adjacent deep regions of the brain (2). A considerable amount of data implicates the cortico-striato-thalamo-cortical circuit in TS pathophysiology, particularly basal ganglia (BG) abnormalities. The BG, a richly interconnected set of nuclei, is essential for the initiation and correct implementation of learned sequences of motor and cognitive segments that characterize purposive behavior. The two major inputs into the BG, from the cerebral cortex and the intralaminar nuclei of the thalamus, enter into the striatum, which consists of the caudate (Cd) and putamen (Pt). The firing of cortical inputs drives activity in both medium spiny neurons (MSNs) (3) and several types of interneurons, including parvalbumin (PV)-positive (PVϩ) GABAergic interneurons (4). Striatal PVϩ interneurons are connected by electrical junctions and form a web of inhibitory synapses throughout the striatum, coordinating the activities of MSNs, and likely increasing their threshold of firing in response to cortical inputs (5, 6). MSNs, which are the large majority of neurons in the striatum, project to the globus pallidus pars interna (GPi), either directly or indirectly via the subthalamic nucleus and the globus pallidus pars externa (GPe). These two pathways can be differentiate...

Cortico-basal ganglia neuronal ensembles bring automatic motor skills into voluntary control and integrate them into ongoing motor behavior. A 5% decrease in caudate (Cd) nucleus volume is the most consistent structural finding in the brain of patients with Tourette syndrome (TS), but the cellular abnormalities that underlie this decrease in volume are unclear. In this paper, the density of different types of interneurons and medium spiny neurons (MSNs) in the striatum was assessed in the postmortem brains of 5 TS subjects as compared with normal controls (NC) by unbiased stereological analyses. TS patients demonstrated a 50-60% decrease of both parvalbumin (PV)+ and choline acetyltransferase (ChAT)+ cholinergic interneurons in the Cd and the putamen (Pt). Cholinergic interneurons were decreased in TS patients in the associative and sensorimotor regions but not in the limbic regions of the striatum, such that the normal gradient in density of cholinergic cells (highest in associative regions, intermediate in sensorimotor and lowest in limbic regions) was abolished. No significant difference was present in the densities of medium-sized calretinin (CR)+ interneurons, MSNs and total neurons. The selective deficit of PV+ and cholinergic striatal interneurons in TS subjects may result in an impaired cortico/thalamic control of striatal neuron firing in TS.

Auditory neuropathy is a hearing disorder characterized by normal outer hair cell function and abnormal neural conduction of the auditory pathway. Aetiology and clinical presentation of congenital or early-onset auditory neuropathy are heterogeneous, and their correlations are not well understood. Genetic backgrounds and associated phenotypes of congenital or early-onset auditory neuropathy were investigated by systematically screening a cohort of 23 patients from unrelated Japanese families. Of the 23 patients, 13 (56.5%) had biallelic mutations in OTOF, whereas little or no association was detected with GJB2 or PJVK, respectively. Nine different mutations of OTOF were detected, and seven of them were novel. p.R1939Q, which was previously reported in one family in the United States, was found in 13 of the 23 patients (56.5%), and a founder effect was determined for this mutation. p.R1939Q homozygotes and compound heterozygotes of p.R1939Q and truncating mutations or a putative splice site mutation presented with stable, and severe-to-profound hearing loss with a flat or gently sloping audiogram, whereas patients who had non-truncating mutations except for p.R1939Q presented with moderate hearing loss with a steeply sloping, gently sloping or flat audiogram, or temperature-sensitive auditory neuropathy. These results support the clinical significance of comprehensive mutation screening for auditory neuropathy.