Table 2 Differential diagnosis of different diseases sharing an acute onset

Congenital TORCH

Infants infected with toxoplasma in utero often do not have obvious symptoms of toxoplasmosis at birth, and then they may gradually develop hepatosplenomegaly, jaundice, anemia, neurological disorders such as intracranial calcifications, hydrocephalus, and microcephaly, as well as complications such as chorioretinitis and learning disabilities.

Maternal infection with rubella virus before 20 weeks of gestation can result in eye defects, congenital heart disease, sensorineural deafness, and central nervous system lesions in infants. The long-term sequelae may include diabetes, precocious puberty, and progressive panencephalitis.

A small proportion of fetal infection with cytomegalovirus in utero can lead to growth restriction, microcephaly, intracranial calcification, hepatosplenomegaly, and long-term sequelae such as sensorineural deafness, visual impairment, psychomotor retardation, and learning disabilities.

Intracranial calcifications appear as linear calcified nodules, which are often accompanied by ventricular enlargement and patchy hypodense shadows in the periventricular white matter. Basal ganglia calcifications are also common and may be accompanied by brain atrophy and microcephaly.

Tuberous Sclerosis Complex

Skin manifestations include facial angiofibroma and hypopigmented macules on the trunk and limbs.

Neurologic symptoms include epileptic seizures often accompanied by intellectual disability. The location of intracranial nodules can cause corresponding focal neurological deficits.

Calcified lesions are often located in the deep white matter of the hemisphere, frequently around the lateral ventricles, especially near the anterior and occipital horns and may be located in the centrum semiovale. Lesions are typically smaller in size (< 1.5 cm), with both new and old lesions being present, and have no surrounding edema or mass effect. They are typically arranged vertically against the ventricular lateral wall (Dawson finger sign) and are consistent with the course of the small blood vessels in the periventricular white matter. MRI is more sensitive than CT in detecting these lesions.

Cerebral Arteriovenous Malformation

Clinical symptoms commonly include cerebral hemorrhage, headache, and epileptic seizures.

Calcifications are typically ring or crescent-shaped, and they are accompanied by localized brain atrophy. Enhancement may be seen on contrast-enhanced scans.

Encephalofacial Angiomatosis (Sturge-Weber Syndrome)

Skin manifestations include flat facial hemangioma at birth, commonly located in the distribution area of the trigeminal nerve on one side of the face. Most of the hemangiomas distributed in the ophthalmic branch were purplish-red hemangiomas. In severe cases, the hemangiomas can spread over one side of the face.

Neurologic symptoms include epileptic seizures, most of which are drug-resistant epilepsy. Mental decline often occurs with the increase of age, and there is a certain correlation between mental decline and the age of onset of the disease. The earlier the onset of the disease, the more likely to have mental decline. Hemiplegia and hemiatrophy may occur on the contralateral side of the cerebral facial hemangioma.

CT may show unilateral or localized brain atrophy, with the calcifications distributed in a gyriform pattern in the occipital and parietal cortex, often unilaterally. Hemangiomas may be present in the facial area ipsilateral to the lesion. MRI shows reticular enhancement of leptomeningeal vascular malformations. The ipsilateral choroid plexus is enlarged and significantly enhanced.

Cerebral Cysticercosis

The major manifestations include seizures, increased intracranial pressure, and meningoencephalitis. Patients may also experience tonic-clonic seizures, complex partial seizures, and other symptoms such as headache, vomiting, hemianopsia, and aphasia. Additionally, psychiatric disorders, paralysis, and cranial nerve palsy may occur.

Imaging findings vary with the stage of the disease and the host response. Typical presentation is in the subarachnoid space, and the cysticerci invasion can involve the cerebral cisterns, brain parenchyma, and ventricles.

Intraventricular cysts are often solitary, with the fourth ventricle being the most common location for calcifications in individuals under 30 years old.

Parenchymal cyst CT shows diffuse cerebral edema with well-defined gray-white matter boundaries, low-density lesions, and small cystic low density shadows, and narrowing of the sulcal fissures as well as the intraventricular system. The contrast-enhanced scans show no enhancement. Some patients may have pericystic edema with partial or complete calcifications. The CT results of the ventricular cysts show ovoid cystic low-density shadows in the enlarged ventricle, resembling cerebrospinal fluid, and small dot-like high-density shadows, which are cerebral cysticercus scoleces. Contrast-enhanced CT scans show no obvious enhancement.

For the last type, that is, meningeal cyst, a hydrocephalus is present via CT, and enhanced CT shows varying degrees of meningeal enhancement reaction.

The MRI manifestations of cerebral cysticercosis are diverse and can be classified into the survival stage and the death stage. The enhanced effect is obvious in the death stage, accompanied by edema. The enhancement is characterized by nodules of uniform size, with few exceeding 2.5 cm.

Neurofibromatosis Type 1

The characteristic feature is the presence of multiple non-malignant nervous system tumors. The two main manifestations are café-au-lait macules on the skin and multiple neurofibromas in the peripheral nerves. Patients may also exhibit symptoms such as epilepsy and learning disabilities.

Intracranial tumors may be associated with meningiomas and can be multifocal. They may also be combined with gliomas and ventricular meningiomas.

CT findings shows non-neoplastic isolated calcifications in the temporal horn choroid plexus or calcifications along the entire choroid plexus. Hypoplasia of the greater wings of the sphenoid bone, combined with herniation of temporal lobe into the orbit and pulsatile proptosis, can be complicated by meningiomas, schwannomas, and gliomas. In terms of the MRI manifestations: (1) bilateral acoustic neuromas, most of which are more severe on one side; (2) multiple neurofibromas of the cranial and peripheral nerves; (3) concomitant meningiomas or gliomas; and (4) often accompanied by skeletal deformities, such as spinal bifida and skull defects.