Characteristics of Conversion Disorder in an Urban Academic Children's Medical Center.

Background. Literature on childhood conversion disorder (CD) is sparse and is mostly limited to the outpatient population. Method. Our study retrospectively examines the characteristics of childhood CD in 42 children and adolescents seen by the psychiatric consultation-liaison service in an urban academic medical center with a large minority population. Results. CD accounted for 11% of our consultations. The majority of patients were female adolescents, but in the younger cohort, the male-to-female ratio equalized. Other somatic symptoms and additional psychiatric diagnoses were common, anxiety disorders in particular. Antecedent stressors were identified in 95% of patients, most commonly related to family stressors. Recent or remote history of abuse was rare. Neurological presentations were complex, with almost half of the patients presenting with multiple distinct neurological symptoms. Hyperkinetic symptoms were more common than hypokinetic symptoms, and paroxysmal symptoms were more common than non-paroxysmal. No distress (la belle indifference) was found in only 25% of patients and about half of patients had no socio-academic impairment. High resource utilization was noted based on multiple specialist consultants, diagnostic studies, and length of stay. Conclusion. Much of our data confirms previous findings and contributes to what is becoming a more robust characterization of this population.

Calcium-dependent inactivation of calcium channels in cochlear hair cells of the chicken.

Voltage-gated calcium channels support both spontaneous and sound-evoked neurotransmitter release from ribbon synapses of cochlear hair cells. A variety of regulatory mechanisms must cooperate to ensure the appropriate level of activity in the restricted pool of synaptic calcium channels ( approximately 100) available to each synaptic ribbon. One potential feedback mechanism, calcium-dependent inactivation (CDI) of voltage-gated, L-type calcium channels, can be modulated by calmodulin-like calcium-binding proteins. CDI of voltage-gated calcium current was studied in hair cells of the chicken's basilar papilla (analogous to the mammalian cochlea) after blocking the predominant potassium conductances. For inactivating currents produced by 2.5 s steps to the peak of the current-voltage relation (1 mm EGTA internal calcium buffer), single exponential fits yielded an average decay time constant of 1.92 +/- 0.18 s (mean +/- s.e.m., n = 12) at 20-22 degrees C, while recovery occurred with a half-time of approximately 10 s. Inactivation produced no change in reversal potential, arguing that the observed relaxation did not result from alternative processes such as calcium accumulation or activation of residual potassium currents. Substitution of external calcium with barium greatly reduced inactivation, while inhibition of endoplasmic calcium pumps with t-benzohydroquinone (BHQ) or thapsigargin made inactivation occur faster and to a greater extent. Raising external calcium 10-fold (from 2 to 20 mm) increased peak current 3-fold, but did not alter the extent or time course of CDI. However, increasing levels of internal calcium buffer consistently reduced the rate and extent of inactivation. With 1 mm EGTA buffering and in 2 mm external calcium, the available pool of calcium channels was half-inactivated near the resting membrane potential (-50 mV). CDI may be further regulated by calmodulin-like calcium-binding proteins (CaBPs). mRNAs for several CaBPs are expressed in chicken cochlear tissue, and antibodies to CaBP4 label hair cells, but not supporting cells, equivalent to the pattern seen in mammalian cochlea. Thus, molecular mechanisms that underlie CDI appeared to be conserved across vertebrate species, may provide a means to adjust calcium channel open probability, and could serve to maintain the set-point for spontaneous release from the ribbon synapse.