Earlier today we introduced you to The Bedside Dysmorphologist: Classic Clinical Signs in Human Malformation Syndromes and their Diagnostic Significance, by William Reardon. Dysmorphology is the study of congenital malformations. This afternoon we have another helpful excerpt, about persistent drooling.
Recognizing the Sign This hardly requires any clinical expertise, but a good history can inform the examination and investigation. The neonatal feeding history will often be of a poor feeding pattern, perhaps requiring nasogastric supplementation. Establish whether there was macroglossia at birth, cleft palate, or micrognathia. Was there any suggestion of velopharygeal incompetence on feeding, often represented by nasal regurgitation of milk during feeding? Gauge the progress of the child with respect to perceptive and expressive speech.
Establishing a Differential Diagnosis Observe the face for evidence of a generalized myopathy and then assess the patient’s muscle bulk generally. Specifically, look at the tongue. Establish whether it looks large and symmetric, erhaps with a deep central groove, which might cause you to consider Simpson-Goabli-Behmel (SGB) syndrome, especially if there was a high birth weight, a history of X-linked mental retardation, and/or cardiac malformations. Evaluate the heart clinically–a murmur will add weight to your diagnostic concern. Cardiac concerns, a history o nasal reguritation of milk on feeding, and speech delay may equate with velo-cardio-facial (VCF) syndrome. Does the tongue look as asymmetric, in which case careful evaluation of the face and limbs for asymmetry is warranted? Does the tongue move normall and specifically assess whether the child protrudes the tongue from the oral cavity? Failure to protrude the tongue with a history of poor feeding and delayed expressive speech is typical of Worster-Drought syndrome. In this condition, examine the lower cranial nerves–often there are signs of pseudobulbar palsy. There may be a striking discrepancy between the general development of the child, which can be within normal paramaters, and the expressive speech, which is greatly delayed. A history of polyhydramnios, an open-mouth appearance, and generalized muscle weakness are the classic hallmarks of congenital myotonic dystrophy. Careful evaluation of the family history may establish cases of symptomatic cataract before the age of 40 years, and maternal examination in this condition will establish corroborative signs, such as myotonia of the thenar eminence on percussion. Transmission of the congenital form is virtually exclusively maternal. Sixth or seventh cranial nerve palsy strongly suggests Moebius syndrome as the underlying diagnosis, in which case limb asymmetry, syndactyly, and brachydactyly should be sought and the pectoral wall muscles be evaluated, since absence is quite comon in this condition.
Investigations to Consider GPC3 gene mutations underlie SGB syndrome, but clinical diagnosis is usually possible. FISH of 22q11 is indicated to establish VCF syndrome. Myotonic dystrophy is demonstrable as a triplet repeat expansion in the MD gene f chromosome 19. Magnetic resonance imaging scan in Worser-Drought cases frequently establishes perisylvian polymicrogyria.