Abstracts

Cortical dysplasia (CD) is the cause of intractable pediatric epilepsy in up to 60% of surgical case series.¹ Previously identified histologic features of CD include large dysmorphic neurons and prominent disorganized neurites. We hypothesize that there are differences in dendrite morphology (total dendrite length and branching patterns) between CD tissue and controls. To better understand the cellular morphology of CD, we quantitatively characterized the dendritic tree of dysmorphic neurons from Palmini grade II A and II B dysplasia from children with refractory epilepsy.², Tissue from pediatric CD patients was collected at the time of epilepsy surgery and stained using the Golgi-cox method. We have analyzed dendrite length and branching order from 3 refractory patients. Dendrites attached to the cell body are first order dendrites and those arising from the first order are called second order dendrites, and so on. Branching order is a measure of the neuron[apos]s dendrite tree complexity. Dendrite length refers to the summed total of the basilar dendritic tree. Slides were analyzed for total dendrite length, and dendrite order for at least 10 neurons per patient and compared against literature autopsy controls.^2,3, Patients 1, 2, and 3 were 11% (461[mu]m [plusmn] 74.7 SEM), 30.3% (1271[mu]m [plusmn] 182.3 SEM) and 17.0% (714.8[mu]m [plusmn] 121.5 SEM) of the total dendrite tree length compared to literature controls (4193.4[mu]m [plusmn] 250 SEM). The most complex of our patients neurons branched to the 5^th order, compared to the 8^th order in controls. The largest difference in branching order occurred in 3^rd and 4^th branches, with Patients 1, 2, and 3 at 8%, 22%, and 2.7% of the control values, respectively, for number of dendrites per cell that branched to a 4^th order., Pediatric CD tissue varied significantly from literature autopsy controls[apos], with shorter total dendrite length per cell and decreased branching, indicating that CD dendrite trees are smaller and simpler in structure. Our findings suggest that the large and disorganized appearance of neurites in type II CD is associated with lack of dendrite organization rather than dysmorphic neurons with enlarged dendrite trees. Our data also suggest the dysmorphic neurons are similar to immature neurons with less complex dendrite trees. We are analyzing autopsy specimens from multiple ages to address this issue.
References:
¹ Neurology. 2003 Aug 12;61(3)365-8.
² Neurology. 2004 Mar 23; 62(6 Suppl 3):S2
³ Cereb Cortex. 2001 Jun; 11 (6):558-71., (Supported by: This work was funded by grants from the Epilepsy Foundation of America for Silvia MT and by the CURE Foundation for Porter BE.)