Apneic Seizures in a Child with Achondroplasia

A 7-month-old female with achondroplasia (FGFR3 c.1138G > A), developmental delay, obstructive sleep apnea (OSA) diagnosed by sleep study, s/p tonsillectomy presented with apneic spells starting at 4 months. Initial electroencephalograms (EEG) were normal but failed to capture apneas. Eventually, a left temporal seizure was captured on video EEG characterized by apnea resulting in cyanosis, unresponsiveness, right-sided eye deviation, lip smacking, and tongue thrusting ([Fig. 1]). Magnetic resonance imaging (MRI) revealed foramen magnum stenosis consistent with stigmata of achondroplasia, frontotemporal atrophy, hippocampal inversion, and deep transverse sulcus ([Fig. 2]). The patient's seizures were treated with low-dose oxcarbazepine and apnea resolved.

Fig. 1 Electroencephalography tracings showing left temporal seizure. (A–D) Evolution of left temporal seizure that clinically resulted in right-sided eye deviation, lip smacking, tongue thrusting, cyanosis, and unresponsiveness.

Fig. 2 Magnetic resonance imaging with foramen magnum stenosis, frontotemporal atrophy, ventriculomegaly, hippocampal inversion, and deep transverse sulcus. (A) sagittal T2 short tau inversion recovery, arrow-foramen magnum stenosis with opisthion overgrowth, (B) coronal T2, solid arrow-incomplete folding with hippocampal inversion, dashed arrow-hippocampal inversion, dysgenesis (C) axial T1, arrow-deep transverse sulcus in the mesial temporal lobe.

Achondroplasia is an inherited autosomal dominant condition with incidence of 0.36 to 0.6 per 10,000 live births.[1] [2] [3] Although apnea in achondroplasia is frequently associated with OSA, craniocervical junction abnormalities, and/or brain stem compression causing central apnea,[1] [2] seizures should be considered as a possible treatable etiology for apneic events,[4] especially in the setting of abnormal neuroimaging. Temporal lobe seizures and temporal lobe abnormalities ([Table 1]) are reported in FGFR3-related disorders, including hypochondroplasia and achondroplasia.[3] [5] Therefore, this case highlights the importance of comprehensive neurological examination, testing with EEG and MRI, and multidisciplinary follow-up including neurology subspecialty services in children with achondroplasia.

Table 1 Brain imaging findings in achondroplasia

Ventriculomegaly

Megalencephaly

Atrophy

Abnormal temporal horns

Deep transverse sulcus

Sagittal cleft

Hippocampal inversion

Oversulcation

Loss of temporal gray-white matter differentiation

Publication History

Received: 27 October 2020

Accepted: 10 December 2020

Article published online:
12 February 2021

• References

• 1 Bodensteiner JB. Neurological manifestations of achondroplasia. Curr Neurol Neurosci Rep 2019; 19 (12) 105
• 2 Stratbucker WB. In brief: Achondroplasia. Pediatr Rev 2009; 30 (03) 114-115
• 3 Manikkam SA, Chetcuti K, Howell KB, Savarirayan R, Fink AM, Mandelstam SA. Temporal lobe malformations in achondroplasia: expanding the brain imaging phenotype associated with FGFR3-related skeletal dysplasias. AJNR Am J Neuroradiol 2018; 39 (02) 380-384
• 4 Lee HW, Hong SB, Tae WS, Seo DW, Kim SE. Partial seizures manifesting as apnea only in an adult. Epilepsia 1999; 40 (12) 1828-1831
• 5 Okazaki T, Saito Y, Ueda R. et al. Epileptic phenotype of FGFR3-related bilateral medial temporal lobe dysgenesis. Brain Dev 2017; 39 (01) 67-71