DDx
Diagnostic Considerations
Bacterial meningitis in neonates almost always occurs with sepsis but is difficult to distinguish clinically from sepsis alone; both present with a constellation of symptoms that indicate systemic illness. Therefore, treatment is started on the basis of presumed infection rather than proven infection. Because the goal in the neonate is to manage any life-threatening condition that will respond to intervention, the differential diagnosis includes disorders of cardiac, pulmonary, and metabolic functions.
Other central nervous system (CNS) problems may present in a manner that simulates meningitis. These include hemorrhage, ischemic stroke, and hypoxic-ischemic encephalopathy. Cerebral edema associated with nonhemorrhagic trauma may present a confounding picture.
In addition, bacterial or viral meningitis always should be considered among the disorders that cause shock, disseminated intravascular coagulation (DIC), or hepatic failure in neonates. However, by the time these conditions develop, the opportunity for successful intervention may have passed. Therefore, prompt consideration of meningitis remains prudent whenever a neonate demonstrates even slight lethargy or irritability.
Other conditions that should be considered are drug withdrawal, inborn errors of metabolism (including aminoacidopathies, organic acidurias, urea cycle disorders, and mitochondrial disease), and gastrointestinal problems such as necrotizing enterocolitis or perforated bowel. The possibility of nonaccidental trauma (ie, shaken baby syndrome) should be taken into account as well.
Differential Diagnoses
Media Gallery
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Acute bacterial meningitis (same patient as in the other two images). This axial nonenhanced CT scan shows mild ventriculomegaly and sulcal effacement.
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Acute bacterial meningitis (same patient as in the other two images). This axial T2-weighted MRI shows only mild ventriculomegaly
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Acute bacterial meningitis (same patient as in the other two images). This contrast-enhanced, axial T1-weighted MRI shows leptomeningeal enhancement (arrows).
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Meninges of the central nervous parts
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Neisseria meningitidis
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Neonate with a lumbar myelomeningocele with an L5 neurologic level. Note the diaphanous sac filled with cerebrospinal fluid and containing fragile vessels in its membrane. Also, note the neural placode plastered to the dorsal surface of the sac. This patient underwent closure of his back and an untethering of his neural placode. The neural placode was circumnavigated and placed in the neural canal. A dural sleeve was fashioned in such a way to reconstruct the neural tube geometry.
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This anteroposterior skull radiograph demonstrates the craniolacunia or Luckenschadel seen in patients with myelomeningocele and hydrocephalus. Mesodermal dysplastic changes cause defects in the bone. The thin ovoid areas of calvaria are often surrounded by dense bone deposits. They are most likely the result of defective membranous bone formation typical of neural tube defects and not increased intracranial pressure as once thought. These characteristic honeycomb changes are seen in about 80% of the skulls in children with myelomeningocele and hydrocephalus
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Sagittal T1-weighted MRI image of a child after closure of his myelomeningocele. Child is aged 7 years. Note the spinal cord ends in the sacral region far below the normal level of T12-L1. It is tethered at the point in which the neural placode was attached to the skin defect during gestation. The MRI showed dorsal tethering, and the child complained of back pain and had a new foot deformity on examination. By definition, all children with a myelomeningocele have a tethered cord on MRI, but only about 20% of children require an operation to untether the spinal cord during their first decade of life, during their rapid growth spurts. Thus, the MRI must be placed in context of a history and examination consistent with mechanical tethering and a resultant neurologic deterioration.
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Sagittal T1 MRI image of a child with a myelomeningocele and associated Chiari II malformation. Note the cerebellar vermis and part of the brainstem has herniated below the foramen magnum and into the cervical canal (arrow). This patient had multiple brainstem symptoms and findings to include stridor and cranial nerve paresis (cranial nerves III, VI, IX, X) despite having a well-functioning ventricular-peritoneal shunt. He required a posterior fossa decompression of his hindbrain in order to relieve the symptoms of hindbrain herniation and brainstem compression. A minority of myelomeningocele patients require a Chiari II decompression. Those that do usually present in their first year of life with similar symptoms, stridor and cranial nerve paresis. A functioning shunt is imperative prior to exploring the posterior fossa in these children. Often times, especially in older children, a shunt revision may alleviate some of the symptoms of hindbrain compression. Tube Defects in the Neonatal Period
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Neonate with a large occipital encephalocele lying in the prone position prior to surgical intervention. Note the large skin-covered sac that represents a closed neural tube defect. Often called cranium bifidum, it is a more serious condition that represents a failure of the anterior neuropore to close. In this patient, a defect in the skull base (basicranium) was associated with this large sac filled with cerebrospinal fluid and a small, disorganized remnant of brain. The patient fared satisfactorily after the surgery in which the encephalocele was excised. However, the patient needed placement of a ventricular-peritoneal shunt to treat the resultant hydrocephalus, which is not uncommon. At age 5 years, the child was doing well and had only moderate developmental delay.
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Autopsy specimen on a child with anencephaly. This is one of the most common CNS malformations in the West. The neonate, like almost all with such a severe forms of neural tube defects, did not survive more than a few hours or days. This malformation represents a failure of the anterior neuropore to close. This photograph also reveals an absence of the calvaria and posterior bone elements of the cervical canal, as well as the deficiency in the prosencephalon. Photo courtesy of Professor Ron Lemire.
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Ventral view of a child with anencephaly that, like the previous picture, shows the loss of cranium and enclosed nervous tissue. In addition to the primary defect in development, a secondary destruction of nervous tissue occurs. Direct exposure to the caustic amniotic fluid causes progressive destruction of the remaining neural structures and secondary proliferation of a thin covering of vascular and glial tissue. Photo courtesy of Professor Ron Lemire.
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These 2 photographs depict the lumbar regions on 2 different children with closed neural tube defects. Both children have lipomyelomeningocele. The child in the left has a dorsal lipoma that is pedunculated. The child on the right has a more common-appearing lipomatous mass that is heaped up beneath the skin. Both lipomas lead from the subcutaneous tissue, through the dura and into the intradural space, where they are attached to the spinal cord. Photos courtesy of Professor J.D. Loeser.
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Photograph of a child undergoing a neurosurgical procedure in which the spinal cord is being detached (untethered) from the intradural and extradural lipomatous mass that fixes it to the subcutaneous tissue. The white arrow shows the laser char on the lipoma that has been shaved off the spinal cord and was connected to the extradural mass. The black arrow shows the extradural lipoma, which crept through the dura and attached to the spinal cord, thereby firmly fixing the spinal cord at too low and too dorsal a location in the sagittal plane.
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The lumbar region of a newborn baby with myelomeningocele. The skin is intact, and the placode-containing remnants of nervous tissue can be observed in the center of the lesion, which is filled with cerebrospinal fluid (CSF).
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Axial T1-weighted MRI scan of an 8-week-old girl who presented with enlarging head circumference. Considerable ventricular dilatation is shown on the lateral and third ventricles. Periventricular lucency is observed around the frontal horns, indicating raised intraventricular pressure.
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Sagittal T1-weighted MRI scan of an 8-week-old girl who presented with enlarging head circumference. The third and lateral ventricles are dilated, whereas the fourth ventricle is of normal size. Aqueductal stenosis is shown. The appearance is typical of this condition.
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Phase-contrast MRI scan of an 8-week-old girl who presented with enlarging head circumference, obtained 3 months after endoscopic third ventriculostomy. A large signal void is shown in the prepontine region, corresponding to the flow through the stoma in the floor of the third ventricle, indicating that the ventriculostomy is functioning well.
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Axial T1-weighted MRI scan of a 15-year-old girl who was born with thoracic myelomeningocele, hydrocephalus, and Arnold-Chiari II syndrome. She was treated with a ventriculoperitoneal shunt. The ventricular system has a characteristic shape, with small frontal and large occipital horns, which are typical in patients with spina bifida. The shunt tube is shown in the right parietal region.
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Sagittal T1-weighted MRI scan of a 15-year-old girl who was born with thoracic myelomeningocele, hydrocephalus, and Arnold-Chiari II syndrome. Significant hindbrain hernia and low-lying fourth ventricle are shown in the context of the Arnold-Chiari II syndrome. Damaged shunt valve removed during shunt revision from a 22-year-old woman with hydrocephalus and spina bifida. The material of the valve has dramatically disintegrated.
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Damaged shunt valve removed during shunt revision from a 22-year-old woman with hydrocephalus and spina bifida. The material of the valve has dramatically disintegrated.
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