Prolonged neuromuscular block associated with cholinesterase deficiency

RATIONALE

Hereditary genetic mutations may cause congenital cholinesterase deficiency. When succinylcholine and mivacurium are applied on cholinesterase-deficient patients during general anesthesia, prolonged postoperative asphyxia occurs, which is an uncommon but very serious complication.

PATIENT CONCERNS

A previously healthy 30-year-old female presented prolonged spontaneous breathing recovery after general anesthesia.

DIAGNOSES

After the patient's postoperative spontaneous breathing recovery delayed, the plasma cholinesterase was found to be 27 U/L, which was far below the normal level (4000 U/L to 13500 U/L). This patient had no disease that can cause plasma cholinesterase deficiency and was therefore diagnosed as congenital cholinesterase deficiency.

INTERVENTIONS AND OUTCOMES

The patient was sent to the intensive care unit (ICU) intubated for mechanical ventilator support, and on the next day the tracheal tube was removed without any complications when her spontaneous respiration resumed.

LESSONS

Cholinesterase is an enzyme secreted by the liver involved in many physiological processes in human body. Plasma cholinesterase commonly contains acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). When succinylcholine and mivacurium are applied on patients with cholinesterase-deficiency during general anesthesia, prolonged postoperative asphyxia occurs, which is an uncommon but very serious complication. Lately, new evidences have suggested that hereditary genetic mutations may be responsible for congenital cholinesterase deficiency.

A lethal association of congenital apnea with brainstem tegmental necrosis

We present a female with premature birth, polyhydramnios, congenital apnea, cranial nerve palsies, orofacial and limb anomalies. Neuroimaging revealed calcifications along the vental margin of the caudal fourth ventricle. Neuropathologic findings at postmortem examination were consistent with brainstem tegmental necrosis and olivary hypoplasia, a rare lethal entity that should be considered in the differential diagnosis of congenital apnea.

Rnx deficiency results in congenital central hypoventilation

The genes Tlx1 (Hox11), Enx (Hox11L2, Tlx-2) and Rnx (Hox11L2, Tlx-3) constitute a family of orphan homeobox genes. In situ hybridization has revealed considerable overlap in their expression within the nervous system, but Rnx is singularly expressed in the developing dorsal and ventral region of the medulla oblongata. Tlx1-deficient and Enx-deficient mice display phenotypes in tissues where the mutated gene is singularly expressed, resulting in asplenogenesis and hyperganglionic megacolon, respectively. To determine the developmental role of Rnx, we disrupted the locus in mouse embryonic stem (ES) cells. Rnx deficient mice developed to term, but all died within 24 hours after birth from a central respiratory failure. The electromyographic activity of intercostal muscles coupled with the C4 ventral root activity assessed in a medulla-spinal cord preparation revealed a high respiratory rate with short inspiratory duration and frequent apnea. Furthermore, a coordinate pattern existed between the abnormal activity of inspiratory neurons in the ventrolateral medulla and C4 motorneuron output, indicating a central respiratory defect in Rnx mice. Thus, Rnx is critical for the development of the ventral medullary respiratory centre and its deficiency results in a syndrome resembling congenital central hypoventilation.

Brainstem tegmental necrosis and olivary hypoplasia: a lethal entity associated with congenital apnea

Previously, we reported an isolated case of a newborn with central apnea at birth, ventilator-dependence, and combined malformative and destructive brainstem lesions (1). We now report 2 additional cases with similar clinicopathologic features. All 3 patients were male (XY karyotype) and required immediate ventilatory support in the delivery room. Perinatal complications included polyhydramnios and breech presentation. Variable cranial nerve palsies and orofacial and limb anomalies were present. The patients dies within minutes of withdrawal of ventilatory support at 2 to 11 weeks after birth. Significant neuropathologic findings were localized to the caudal pons and medulla, and included tegmental necrosis (neuronal loss, gliosis, mineralization) with involvement of respiratory-related nuclei, and anomalies of rhombic lip derivatives (olivary hypoplasia, arcuate nucleus hyperplasia). Three-dimensional computer reconstructions facilitated clinicoanatomic correlations, and underscored the restriction of the lesions to pontine and medullary rhombomeres and rhombic lip. The histopathology of these cases suggests a malformative process occurring at the end of the first trimester (time of rhombic lip migrations), and a superimposed destructive process (tegmental necrosis) in the second half of gestation. Although the etiology is unknown, the segmental nature of the lesions suggests the possibility of an abnormality in homeobox gene regulation. These cases likely represent a distinct clinicopathologic entity that should be considered in the differential diagnosis of Moebius syndrome and failure to breathe at birth.

Congenital apnea with medullary and olivary hypoplasia: a pathologic study with computer reconstructions

We report a three-month-old infant with congenital central apnea who was ventilator-dependent throughout his brief life. At autopsy the most significant findings were localized to the medulla and included severe tegmental necrosis involving respiratory-related sites and olivary hypoplasia. Golgi impregnations of the cerebellum demonstrated several Purkinje cells with changes consistent with experimental olivary ablation. The majority of Purkinje cells, however, were normal; this observation suggests that in an early and subtotal olivary lesion, the incomplete complement of olivary neurons maintains sufficient collateral axonal branches to compensate for decreased cell number. Computer graphics enabled us to dissect the components of the complex medullary pathology and examine them individually and in selected combinations in three dimensions. Computer reconstruction aided the identification and dating of a malformative lesion (first trimester) from a later (second/third trimester), superimposed destructive lesion. This report suggests that the synthesis of complex morphologic data in human neuropathology into meaningful three-dimensional visual displays by computer reconstruction facilitates their comprehension. Computer reconstruction is especially valuable in the elucidation of 3-D topographic relationships in functionally and architecturally complex regions such as the brain stem.

Medullary nuclear dysplasia (Möbius syndrome) in an infant with recurrent apnea and isoelectric EEG

From birth, an infant girl had repeated episodes of loss of consciousness, apnea and bradycardia, aphonia, and severe pharyngeal-esophageal discoordination. These functional deficits correlated with a gross and microscopic malformation of the medulla oblongata, which is characterized by profound deficits of motor and sensory nuclei and of the reticular formation. We have classified this as an example of Möbius syndrome. No etiology was suggested from the history. Histopathologic findings are compatible with an early massive insult to developing structures in the tegmentum of the medulla oblongata.