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Biomedical subjects

A K Afifi

Publications and source records attributed to A K Afifi.

At least 19 recordsLinked to original sources
PubMed2001

Childhood Guillain-Barré syndrome: clinical and electrophysiologic features predictive of outcome.

The hospital records of 27 children with the diagnosis of Guillain-Barré syndrome were retrospectively reviewed. Based on the time to recovery, patients were divided into two groups: group 1 consisted of children whose times to complete or partial recovery extended beyond 2 months from onset of the disease; group 2 consisted of children who attained a full recovery within 2 months from onset of the disease. The clinical and electrophysiologic features of the two groups were statistically compared for their predictive value of outcome. Three clinical features (maximum disability score at presentation, intubation, and cranial nerve involvement) were predictive of poor outcome, whereas one electrophysiologic feature (conduction block) was predictive of favorable outcome. There was also a significant correlation between maximum disability score at presentation and the probability of intubation.

Adolescent↗
PubMed2001

Optic neuritis: a novel presentation of Schilder's disease.

The clinical features of a 7-year-old girl who presented with unilateral optic neuritis are presented. Magnetic resonance imaging (MRI) showed lesions in the affected optic nerve and the centrum semiovale bilaterally. Biopsy of one of the cerebral lesions was consistent with a diagnosis of Schilder's disease. Visual acuity returned to normal, and the demyelinating MRI lesions improved markedly with corticosteroid treatment. Optic neuritis is a novel mode of presentation in Schilder's disease.

Biopsy↗
PubMed1998

Presentation, management and follow-up of Schilder's disease.

Schilder's diffuse myelinoclastic sclerosis is a rare demyelinating disease which often mimics intracranial neoplasm or abscess. We have treated 3 patients with this disorder in the past 5 years and followed their postoperative course. Certain distinct features of this disease will allow neurosurgeons to preoperatively entertain this diagnosis. We discuss postoperative treatment and propose a new hypothesis regarding the variable prognoses of this disorder. Schilder's disease constitutes an important diagnosis for any neurosurgeon to be aware of (especially those treating the pediatric age group) which has not received adequate coverage in the neurosurgical literature.

Adolescent↗
PubMed1994

Basal ganglia: functional anatomy and physiology. Part 1.

Advances in knowledge about basal ganglia structure and connectivity from 1925 to date are reviewed. Current concepts about neuronal populations, transmitters, and input and output of each of the basal ganglia nuclei are presented. The portrayal by Wilson, in 1925, of the striatum as a simple homogeneous structure has been replaced by the recognition, based on staining characteristics, connectivity, and function, that the neostriatum is compartmentalized into striosomes, matrisomes, and matrix compartments. Electrophysiologic studies have further shown the existence, in the neostriatum, of neuronal clusters that represent basic functional units much like the functional columns described much earlier for the cerebral cortex. Whereas the neostriatum is considered the major receiving area of the basal ganglia, the globus pallidus and substantia nigra pars reticulata constitute the major output nuclei. Combined neuroanatomic and neurophysiologic studies have revealed precise somatotopic organization throughout the basal ganglia system such that the leg, arm, and face areas of the cerebral cortex related to respective topographic areas within the striatum, pallidum, substantia nigra, and subthalamus. The previous concept of an inhibitory role for dopamine on striatal neurons has been modified. It is now acknowledged that dopamine exerts an inhibitory effect on striatal neurons that project to the external pallidum and a facilitatory effect on striatal neurons that project to the internal pallidum and substantia nigra pars reticulata. The previous concept of serial connectivity of the neostriatum (funnel concept) has been replaced by the concept of parallel connectivity. Within the internal connectivity of the basal ganglia, there is a fast system in which the neurotransmitter is gamma-aminobutyric acid (GABA) and a slow system modulated by neuropeptides. The slow system is believed to give identity to an otherwise homogenous GABAergic system.

Basal Ganglia↗
PubMed1994

Basal ganglia: functional anatomy and physiology. Part 2.

Advances in knowledge about basal ganglia function and circuitry are reviewed. Despite the voluminous available literature on this subject, the role of basal ganglia in health and disease remains controversial. Experimental data on the effects of stimulation and ablation of the basal ganglia are summarized. The roles of the basal ganglia in the preparation for and execution of cortically initiated movement are described. Newer roles ascribed to the basal ganglia in sensory-motor gating, cognition, emotion, and motivation are discussed. The old and current concepts of information flow between the cerebral cortex, striatum, pallidum, thalamus, and back to the cerebral cortex are reviewed. The "funnel" system of information flow has been discarded in favor of several parallel and largely segregated loops pertaining to motor, oculomotor, cognitive, and limbic functions. The anatomic substrate of each of these loops is described. The specific roles of the striatum, pallidum, substantia nigra, and thalamus in information flow as related to movement are described. The roles of the basal ganglia in reinforcing wanted behavior and suppressing unwanted behavior via direct and indirect striatal loops are discussed. The implications of these loops in the genesis of Parkinson's disease and Huntington's chorea are described. Alteration in basal ganglia neurotransmitters and neuromodulators in Huntington's chorea, Tourette's syndrome, and Parkinson's disease are described.

Basal Ganglia↗
PubMed1994

Myelinoclastic diffuse sclerosis (Schilder's disease): report of a case and review of the literature.

The clinical, neuroimaging, and neuropathologic features of Schilder's disease in a 17-year-old girl are presented and compared to 11 well-documented cases reported since 1912. The evolution of knowledge about Schilder's disease and the confusion in nomenclature are reviewed. Signs and symptoms in this case and others reported in the literature are nonspecific and may mimic mass lesions. Neuroimaging studies also may mimic brain tumor or abscess; however, the absence of significant edema, the irregular and incomplete ring enhancement, the discrepancy between size of the lesions and the associated mass effect, and the absence of other lesions elsewhere in the brain may help differentiate Schilder's disease from neoplasm, infection, and other demyelinating lesions. Although frozen sections of these lesions are often interpreted as astrocytoma, the inflammatory, primarily histiocytic, nature of Schilder's disease is more easily recognized in paraffin-embedded material. Unique features of this case include multiple unilateral lesions and the cyst-like degeneration present in both lesions. Multiple lesions in Schilder's disease are characteristically bilateral. The examination of aspirated fluid is the first such report in Schilder's disease. The limitation of multiple lesions in our case to one hemisphere calls for reexamination of the restrictive 1985 criteria of Poser for the diagnosis of Schilder's disease.

Adolescent↗
PubMed1993

Tests for juvenile myasthenia gravis: comparative diagnostic yield and prediction of outcome.

The clinical picture, family history, laboratory data, treatment modalities, and outcome in 27 juvenile myasthenics seen over a 25-year period are presented. Onset was after 10 years of age in the majority of patients. Half presented with ocular signs, the other half with generalized-onset myasthenia. Half of those with ocular-onset myasthenia progressed to generalized myasthenia. The female-to-male ratio was 3.5:1. Myasthenia gravis was reported in the mother of one patient. Ptosis was the most common presenting sign. It was unilateral at onset in 33% of patients and remained unilateral in 11%. Pharmacologic tests (neostigmine methylsulfate and edrophonium chloride) were positive in 92% of patients. Serology was positive in 63%, whereas repetitive nerve stimulation was positive in 33% when distal nerves were stimulated and in 66% when proximal and distal nerves were stimulated. Seropositivity tended to increase with generalization of the myasthenic process. No statistically significant difference in seropositivity was noted between males and females. Anti-striated muscle antibodies were detected in two patients, neither of whom had thymoma. The yield of repetitive stimulation increased with generalization of the myasthenic process and when proximal nerves were stimulated. No statistically significant difference was noted in the decremental response between seropositive and seronegative patients. The majority of ocular myasthenics were treated with pyridostigmine bromide monotherapy. With generalization of the myasthenic process, other modes of medical and surgical therapies were needed. All patients given corticosteroids ultimately underwent thymectomy. The mean age at presentation and the duration of symptoms at presentation were longer in thymectomized patients than in those without thymectomy.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

Etiology of lateral rectus palsy in infancy and childhood.

The etiologies of lateral rectus palsy in 132 infants and children seen over a period of 22 years in a university medical center were retrospectively reviewed and compared with similar reports in the literature. Unlike most reports, which lump children with adults, this study focuses on childhood etiologies of lateral rectus palsy. In contrast to the only two studies in the literature on childhood lateral rectus palsy, which reflect a purely ophthalmologic perspective, this study reflects experiences of pediatric neurology and pediatric neurosurgery, as well as ophthalmology. Most lateral rectus palsies were unilateral, almost equally distributed between right and left sides. Trauma, tumor, and congenital etiologies were the most prevalent. The relative frequency of each of these etiologies varies by service (neurology, neurosurgery, ophthalmology). In 10.6% of patients, etiology could not be determined. The majority of patients had an isolated lateral rectus palsy. Association of lateral rectus palsy with other cranial nerve palsies and/or long tract signs characterized trauma and tumor. The majority of tumors were primary and infratentorial. A small number of patients had benign recurrent lateral rectus palsy.

Abducens Nerve↗
PubMed1992

Predictive value of electromyography in diagnosis and prognosis of the hypotonic infant.

To investigate the diagnostic validity of electromyography in the hypotonic infant, 79 children aged 0 to 12 months, seen over a 20-year period, were studied retrospectively. The diagnoses using clinical, muscle biopsy, and laboratory characteristics were: 25 central hypotonia, 20 spinal muscular atrophy, 20 myopathy, four myotonic dystrophy, four benign congenital hypotonia, two congenital muscular dystrophy, two myasthenia gravis, one infantile inflammatory myopathy, and one arthrogryposis multiplex congenita. Using strict criteria, electromyography accurately predicted the final diagnosis in 65% of infants with spinal muscular atrophy and was consistent with the diagnosis in another 25%. In contrast, electromyography accurately predicted the final diagnosis in only 10% of infants with myopathy and was normal in 88% of infants with central hypotonia. In infants with spinal muscular atrophy, there was no difference in the predictive value of electromyography when performed in the newborn compared to older infants. Normal distal nerve conduction velocities in infants with spinal muscular atrophy may predict prognosis, since these infants had a longer survival. Electromyography thus has a high predictive value for infantile spinal muscular atrophy but not for myopathy.

Biopsy↗
PubMed1991

Brain tumors occurring before 1 year of age: a retrospective reviews of 22 cases in an 11-year period (1977-1987).

Congenital brain tumors have been reported infrequently and their management remains ill defined. An 11-year review (1977-1987) of all children with brain tumors with the onset of symptoms before 1 year of age was completed. Twenty-two children with the following histological diagnoses were treated: astrocytoma (7 patients), primitive neuroectodermal tumor (6 patients), papilloma or carcinoma of the choroid plexus (3 patients), malignant teratoma (2 patients), dermoid tumor (2 patients), embryonal rhabdomyosarcoma (1 patient), and chloroma (1 patient). Fifteen tumors were supratentorial in location, and 7 were infratentorial. Initial symptoms were hydrocephalus (32%), focal neurological deficit (23%), asymptomatic increase in head circumference (18%), failure to thrive (14%), and seizures (4.5%). The goal of treatment was a radical excision when possible, with primary chemotherapy in the last 6 years of the review period. Radiation therapy was the adjunct to surgery in the initial 5-year period. All patients with papillomas of the choroid plexus and dermoid lesions underwent a total resection with no recurrence. All 7 astrocytomas were supratentorial, with 6 occurring in the diencephalon. Five of the seven patients with astrocytomas survived more than 5 years. The 6 primitive neuroectodermal tumors were located equally between the supra- and infratentorial spaces. Four of the 6 infants with these tumors received chemotherapy (2 received chemotherapy alone; 2 received chemotherapy and radiation therapy) and are tumor free 2 to 9 years later. A fifth child received radiation therapy alone early in the series and survived only 4 months. The family of the other child refused adjunctive treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Astrocytoma↗
PubMed1990

Seizure-induced miosis and ptosis: association with temporal lobe magnetic resonance imaging abnormalities.

Two patients with seizure-associated miosis and ptosis are described. In both there are magnetic resonance imaging abnormalities of the temporal lobe. In one patient, increased magnetic resonance imaging signal intensity is present in the temporal lobe contralateral to ptosis and miosis. In the other, there is temporal lobe asymmetry with the smaller temporal lobe ipsilateral to the miotic pupil and ptotic lid. The relevant human and experimental literature related to cortical control of pupil size and lid movement is reviewed. Based on the available literature and the findings in these two patients, it is proposed that the increased signal intensity in the temporal lobe of one patient represents an irritative stimulus causing contralateral miosis and ptosis, whereas the temporal lobe hypoplasia in the second patient permitted impulses from the contralateral normal temporal lobe to predominate, resulting in miosis and ptosis homolateral to the hypoplastic temporal lobe.

Adolescent↗
PubMed1990

Computed tomography and magnetic resonance imaging of the brain in Hurler's disease.

Computed tomographic (CT) and magnetic resonance imaging (MRI) scans of the brain in five patients with Hurler's disease are described and compared to the few available reports in the literature. Computed tomographic scans revealed low attenuation areas in the centrum semiovale and peritrigonal white matter. Ventriculomegaly was not a prominent feature in our patients, compared to those previously reported. In two patients, CT were normal. The most prominent magnetic resonance imaging abnormalities were the presence of radially oriented cystic areas in the centrum semiovale, peritrigonal white matter, corpus callosum, and pericallosal region. Magnetic resonance imaging abnormalities were present in all patients, even when CT scans were normal. Abnormalities on CT and MRI scans tended to be more prevalent in the posterior regions. Magnetic resonance imaging proved to be a more reliable imaging method in Hurler's disease. T1-weighted images delineated the cystic areas more clearly, whereas T2-weighted images were more sensitive in detecting small white-matter abnormalities. Magnetic resonance imaging abnormalities correlated well with known neuropathologic alteration in this disease. It is suggested that the cystic areas seen on MRI correspond to perivascular lacunae seen in histopathologic material.

Brain↗
PubMed1989

Autosomal recessive cerebellar hypoplasia.

Cerebellar hypoplasia is found in association with a variety of neurologic and systemic disorders. It is the primary finding in the uncommonly reported condition of autosomal recessive cerebellar hypoplasia. We describe two siblings with cerebellar hypoplasia documented in both by magnetic resonance imaging (MRI) and review the clinical features of previously reported cases of autosomal recessive cerebellar hypoplasia. The most common findings in this disorder are nonprogressive ataxia, strabismus, mental retardation, and speech delay with dysarthria. Previously reported cases have been confirmed by autopsy, pneumoencephalography, or computed tomographic (CT) scans. MRI clearly documents diffuse cerebellar hypoplasia and aids in distinguishing autosomal recessive cerebellar hypoplasia from other disorders. The pathophysiology of this disorder is uncertain, however, studies of the weaver mutant mouse (an animal model of autosomal recessive cerebellar hypoplasia) suggest that an abnormality of the Bergmann glia may lead to the observed granule cell layer deficiency in these patients. This diagnosis should be considered for children with nonprogressive ataxia and families should be made aware of the 25% recurrence risk.

Cerebellar Diseases↗