What is Focal Cortical Dysplasia?
Focal cortical dysplasia (FCD) is a malformation of cortical development, which is the most common cause of medically refractory epilepsy in the pediatric population and the second/third most common etiology of medically intractable seizures in adults. In general, three types of cortical dysplasia are recognized.
FCD Type I
a – focal cortical dysplasia with abnormal radial cortical lamination
b – focal cortical dysplasia with abnormal tangential 6-layer cortical lamination
c – focal cortical dysplasia with abnormal radial and tangential cortical lamination
FCD Type II
a – focal cortical dysplasia with dysmorphic neurons
b – focal cortical dysplasia with dysmorphic neurons and balloon cells
FCD Type III
a – architectural distortion of cortical layer in temporal lobe with hippocampal atrophy
b – architectural distortion of cortical layer adjacent to glial or glioneuronal tumor
c – architectural distortion of cortical layer adjacent to vascular malformation
d – architectural distortion of cortical layer adjacent to other lesions acquired in early childhood such as trauma, ischemic event, encephalitis
Epilepsy is the main symptom of FCD, sometimes associated with intellectual disability, particularly with early seizure onset. There are no significant neurological deficits despite large areas of brain tissue occupied by a lesion. Symptoms can appear at any age, generally appearing in childhood. Epilepsy is usually drug-resistant.
Patients with FCD type II typically start showing symptoms earlier than with type I. Earlier onset is also seen in patients with a larger focus on brain MRI as compared to patients with smaller lesions. Seizures with early onset in neonatal period or childhood are more likely FCD type II with multilobar or hemispheric lesion, while FCD type I with a small focus, usually in the temporal lobe, predominates in adults.
Epileptic seizures in focal cortical dysplasia are difficult to control with medication and often intractable. Surgery appears to be a next therapeutic procedure. The resection of lesion, lobectomies and even hemispherectomies are performed. More limited surgeries are performed in elderly patients, usually due to FCD type I, usually located within the temporal lobe. Younger patients typically have FCD type II, with more extensive lesions and extratemporal location, predominantly in the frontal areas. In these cases operation includes lobectomy/ies or even hemispherectomy.
1. Blümcke I, Thom M, Aronica E, Armstrong D, Vinters HV, Palmini A, et al. The clinicopathologic spectrum of focal cortical dysplasias: a consensus classification proposed by an ad hoc Task Force of the ILAE Diagnostic Methods Commission. Epilepsia 2011; 52: 158-74.
2. Kabat J, Krol P. Focal Cortical Dysplasia-review. Polish Journal of Radiology 2012; 77(2): 35–43.