Oscar Papazian

Topical Review Article: Transient Neonatal Myasthenia Gravis

Transient neonatal myasthenia gravis is a postsynaptic neuromuscular transmission defect occurring in 21% of infants born to women with active (and, less commonly, in remission) acquired myasthenia gravis. Although passive-transfer acetylcholine receptor (AChR) antibodies are found in the majority of these newborns, their pathogenic role is questionable because only some infants are symptomatic. Pathogenesis in infants without AChR antibodies is unknown. There is still no biologic marker for prenatal identification of this subpopulation of newborns, although HLA typing may be a promising tool. Sucking, swallowing, and respiratory difficulties are the most common presenting signs in the first day of life. Final diagnosis is done when administration of acetylcholinesterase agents transiently corrects the neuromuscular transmission defect. Serum AChR antibody titers follow the same pattern as their mothers. Supportive management and anticholinesterase agents prior to feedings are necessary in about 80% of patients. In the majority of infants the condition resolves spontaneously. (J Child Neurol 1992;7:135-141).

Focal upper extremity neuropathy in neonates

Focal upper extremity neuropathies are common in neonates. The brachial plexus is the most common site involved. Brachial plexus injuries may involve different structures, thus producing different clinical presentations: complete brachial plexus palsy, Duchenne-Erb palsy, upper-middle trunk brachial plexus palsy, Klumpke palsy, fascicular brachial plexus palsy, and bilateral brachial plexus palsy. The causes of brachial plexus palsy are obstetric injury, intrauterine compression, humeral osteomyelitis, hemangioma, exostosis of the first rib, neck compression, and neoplasm. The differential diagnosis of brachial plexus palsy includes pseudoparesis, amyoplasia congenita, congenita varicella syndrome, and neurological lesions at other neuroanatomical levels. The cause and the degree of injury dictate the prognosis. The prognosis of obstetric brachial plexus injury is usually good.

Cervicothoracic Extradural Arachnoid Cyst: Possible Association With Obstetric Brachial Plexus Palsy

The association of cervicothoracic extradural arachnoid cysts and obstetric brachial plexus palsy has not previously been reported. We report two patients with this association. The first patient is a 9-month-old boy with left obstetric brachial plexus palsy that developed bilateral leg weakness at 6 months of age owing to compression of the spinal cord by a C6 to T8 left cervicothoracic extradural arachnoid cyst. The second patient is a 3-year-old girl with bilateral brachial plexus palsy and spastic paraparesis who had magnetic resonance imaging at 3 days of age that showed intraspinal cord injury and a cervicothoracic extradural arachnoid cyst compressing the spinal cord. We believe that the association of cervicothoracic epidural arachnoid cysts and obstetric brachial plexus palsy in these patients was causal and recommend that the possibility of a cervicothoracic epidural arachnoid cyst be considered in patients with brachial plexus palsy and evidence of spinal cord injury. (J Child Neurol 2002;17:770—772).

Intravenous Valproate Dosing in Neonates

The loading dosage of intravenous valproate required to achieve a desired serum concentration in neonates is not known. Two neonates with seizures received loading doses of intravenous valproate over 30 minutes. Serum valproate concentrations were measured 45 minutes and 3 hours after initiation of the infusion. Both neonates had received phenobarbital and phenytoin before the loading infusions. In the first patient, a loading dose of intravenous valproate of 10 mg/kg increased the 45-minute postinfusion serum valproate concentration to 41 μg/mL with a 3-hour postinfusion serum valproate concentration of 33 μg/mL. In the second patient, a loading dose of 25 mg/kg increased the 45-minute postinfusion serum valproic acid concentration to 100 μg/mL with a 3-hour postinfusion serum valproic acid concentration of 78 μg/mL. We found that each 1 mg/kg of intravenous valproate increased the 45-minute and 3-hour postinfusion serum valproic acid concentrations by approximately 4 μg/mL and 3 μg/mL, respectively. We suggest that these figures be used to calculate the desirable loading dose of intravenous valproate in neonates until larger studies are conducted. The volume of distribution and the serum clearance of valproate were approximately 0.245 L/kg and 25 mL/h/kg, respectively. (J Child Neurol 2000;15:827-829).

Neurophysiological evaluation of children with traumatic radiculopathy, plexopathy, and peripheral neuropathy.

Neurophysiological evaluation of children with traumatic peripheral nervous system injury is accomplished with electromyography, motor and sensory nerve conduction studies, and somatosensory and motor-evoked potentials. Preoperative neurophysiological tests are performed if motor deficits persist for more than 3 months. Evidence of reinnervation on these neurophysiological tests predates clinical recovery by weeks, hence they help determine the site of the lesion and provide objective measures for selecting candidates for surgical exploration. Intraoperative neurophysiological tests help to identify and confirm the integrity of nerves and to develop the optimal surgical strategy. Postoperative evaluations every 3 to 6 months may determine efficacy of treatment.

Control of Spasticity and Involuntary Movements – Cerebellar Stimulation

By stimulating the medial aspect of the superior surface of the cerebellum with relatively short, low current stimulating pulses, spasticity and some involuntary movements have been reduced. Voluntary movements, as a result, are able to come through better; however, if the child has little voluntary ability, he is at least more relaxed, thus allowing the parents to care for him more easily. The children and adults with cerebral palsy have not been transformed from their previous status, although CCS has allowed them to become more independent, more ambulatory, and more communicative.

Similar brain spect findings in subclinical and clinical seizures in two neonates with hemimegalencephaly

Brain single-photon emission computed tomography (SPECT) findings during clinical and subclinical seizures were compared in two neonates with hemimegalencephaly. Interictal and ictal brain SPECT were performed in two neonates. The ictal studies were performed during a clinical seizure in one neonate and during a subclinical seizure in another neonate. They revealed similar focal hemispheric hyperperfusion at the electroencephalographic seizure foci in both cases. The similar perfusion patterns imply that clinical and subclinical seizures place similar metabolic demands on the cerebral tissue involved in the generation of electroencephalographic seizures in neonates with cerebral dysgenesis and suggest that clinical and subclinical seizures should be treated similarly in this population.

Bilateral tonic-clonic epileptic seizures in non-benign familial neonatal convulsions

We report an electroclinical pattern considered characteristic of benign familial neonatal convulsions (BFNC) in two neonates without BFNC. Both neonates were products of uncomplicated pregnancies, labor, and deliveries. The cause of the seizures was not established. There was no family history of seizures or epilepsy. Seizures started on the second and third days after birth. Ten seizures were captured by continuous video-EEG telemetry. The electroclinical events began with generalized tonic posturing coinciding with the appearance of diffuse attenuation of the EEG activity. After several seconds, bilateral clonic movements accompanied by bilateral repetitive sharp waves or spikes occurred in the EEG. One patient had normal development; the other became autistic. We conclude that the electroclinical pattern occurring in BFNC can occur in other types of neonatal seizures.

Bilateral Decreased Oxygenation During Focal Status Epilepticus in a Neonate With Hemimegalencephaly

Early surgical removal of a dysplastic hemisphere appears to be beneficial for neonates with hemimegalencephaly and medically resistant seizures. We analyzed the changes in the cerebral regional oxygen saturation index in a neonate with tuberous sclerosis and right hemimegalencephaly (1) during seven episodes of right hemisphere electroencephalographic status epilepticus with and without clinical manifestations and (2) after right hemispherectomy. The cerebral regional oxygen saturation index demonstrated marked fluctuations and progressive decline in both hemispheres during the episodes and normal values in the remaining hemisphere after surgery. We speculate that decreased oxygenation of the nonepileptic cerebral hemisphere in patients with hemimegalencephaly and medically resistant seizures can contribute to the production of global neurologic impairments in these patients and that the benefits of early hemispherectomy are due to the improved oxygenation of the nondysplastic hemisphere following surgery. (J Child Neurol 2004; 19:394-396).

Single Photon Emission Computed Tomographic Evaluation of Brainstem Release Phenomenon and Seizure in Neonates

We report the ictal brain single photon emission computed tomographic (SPECT) findings in two neonates. One neonate had hypoxic-ischemic encephalopathy, a disorganized discontinuous electroencephalogram (EEG) background, lethargy, seizures, and brainstem release phenomena. A brain SPECT was performed during a brainstem release phenomenon characterized by a 34-second sustained tonic posture of the right arm and chewing. It did not reveal focal cerebral hemisphere hyperfusion. The second neonate had hemimegalencephaly, low-voltage irregular EEG background, and seizures. A brain SPECT was performed during a seizure characterized by a 32-second sustained tonic posture of the right arm. It revealed focal hyperperfusion in the posterior region of the left hemisphere. The brain SPECT findings in these patients indicate that despite clinically similar events, brainstem release phenomena and seizures have different perfusion characteristics, and refute the theory that brainstem release phenomena are due to epileptic foci in the cerebral hemispheres undetectable by EEG. (J Child Neurol 2000;15:56-58).