Knobloch Syndrome

An inherited disorder characterized by encephalocele, vitroretinal degeneration with retinal detachment, high myopia, and normal intelligence. Because all patients have normal intelligence, it is suggested that the cephalocele is a meningocele rather than an encephalocele.

Vitreoretinal Degeneration with Retinal Detachment, and Occipital Cephalocele; Knobloch-Layer Syndrome; Retinal Detachment and Occipital Encephalocele Syndrome.

Approximately 35 patients have been reported in the literature.

Autosomal recessive, caused by defective collagen XVIII. Gene map locus is 21q22.3. Penetrance seems to be 100%; however, variability (intraand interfamilial) is considerable.

Condition controlled by a mutation in the COL18A1 collagen gene that is of variable expressivity. The cranial and eye alterations in this syndrome may occur early in embryogenesis, suggesting that developmental genes may be involved in the pathogenesis of this syndrome.

Made based on the clinical findings. Histology may reveal heterotopic neuronal tissue in the skull lesions (thereby distinguishing between scalp defect and encephalocele).

The most common findings are high myopia, vitreoretinal degeneration with retinal detachment, and occipital encephalocele. Intellegence is usually normal. This led to the assumption, that in many cases the encephalocele may in fact be either a meningocele or a scalp defect. Heterotopic neuronal tissue could be found in the scalp lesions of some patients. Other reported, but inconstant findings include Scimitar Syndrome, patent ductus arteriosus, single umbilical artery, mild congenital pulmonary lymphangiectasia (visible on chest radiographs as interstitial changes), and abnormal palmar creases.

A complete history and thorough examination is required. Ask about pulmonary problems (respiratory distress, cyanosis, cough) and rule out encephalocele (important for positioning of the patient).

If an occipital encephalocele/ meningocele is present, induction of anesthesia is best performed in the left lateral position or alternatively on bolsters avoiding any pressure on the lesion. Congenital pulmonary lymphangiectasia is often fatal in the neonatal period; respiratory distress has not been described in these patients, which probably indicates a mild form of congenital pulmonary lymphangiectasia. However, the threshold for a chest radiograph and/or an arterial blood gas analysis should be kept low. Increases in intraocular pressure should be avoided in patients at risk for retinal detachment.

Since succinylcholine is known to potentially increase intraocular pressure, it should best be avoided in these patients with a high risk of retinal detachment.

Meckel-Gruber Syndrome (MKS): Autosomal recessive disorder characterized by the presence of renal cysts, developmental anomalies of the central nervous system (e.g., posterior encephalocele most often defined as an occipital scalp defect), hepatic ductal dysplasia and cysts, and polydactyly.