Hino-Fukuyo et al. found that the overall prevalence of POR in Asian populations was approximately 5.3 per 100,000 live births (2). Several studies in the United States and European countries suggest that the prevalence of POR at birth is 3.5 per 100,000 live births (3). Therefore, this phenomenon indicates that the prevalence of POR is rare worldwide and the survival rate is low.

Some expert studies believe that most cases of POR are caused by vascular lesions, which is a type of post-migratory stroke, which causes the area of tissue necrosis within the fissure to be absorbed, leaving a lesion of a foramen cyst (4, 5). In rare cases, infection or traumatic injury may also lead to the development of POR, and there have even been reports of a pregnant woman with carbon monoxide poisoning resulting in a child born with a POR (5). In this case, we found that the patient had left upper side weakness and unsteady holding at 2 months of age, and there was no abnormality in the perinatal history. Then the complete brain MRI showed that the right cerebral hemisphere was absent, and no cerebral gray matter tissue was found in the brain fissure, and the missing side was a cyst filled with cerebrospinal fluid. Therefore, we consider that this patient is likely to have stroke symptoms following brain neuron migration, which in turn leads to the formation of POR.

On the other hand, a small number of experts believe that there is phenotypic diversity in COL4A1 mutations, which is one of the important causes of POR. However, COL4A1 mutations can cause not only familial cases of POR, but also a large proportion (approximately 21%) of sporadic cases (6, 7). Therefore, in the process of genetic counseling and examination of POR, once there is a case related to COL4A1 mutation, we need to pay more attention to its family heritability.

POR can occur in any cerebral lobe, but is typically unilateral, with bilateral POR being even rarer; moreover, the clinical manifestations of POR vary significantly depending on their size, ranging from small focal lesions within a lobe to massive lesions occupying an entire cerebral hemisphere (8, 9). When POR occupies the temporal lobe or a region of the hippocampus or leads to conditions such as hippocampal sclerosis, epileptic seizures are among the most likely clinical presentations to occur (10). Researchers have also found that patients with POR may experience various types of epileptic seizures, mental illnesses (such as intellectual disability, delusions, apathy, or persecution complex), motor disorders (including hemiparesis, limb spasticity, or ataxia), as well as diplopia and cerebrospinal fluid leakage among other conditions, with different types of epileptic seizures being the most common. Consequently, some patients are diagnosed with this congenital disorder only after being admitted to the hospital for epileptic seizures (11–13). In this case, imaging revealed a large POR on the right side; the patient first experienced epileptic seizures around the age of ten. Additionally, as the patient aged, there was a gradual decline in cognitive functions and intelligence; these symptoms indicate that the presence of abnormal neurodevelopment in POR may have a pathologically plastic effect on symptom presentation.

Cranial MRI serves as the gold standard for diagnosing POR. Within cranial MRI images, not only can the location of POR abnormalities be precisely identified, but it is also possible to distinguish whether these are cysts filled with cerebrospinal fluid or the formation of partial cavities. The primary manifestation of POR in most patients involves cystic lesions within the brain, which, across all cranial MRI sequences, adhere to the signal characteristics of CSF and demonstrate connectivity with the ventricular system or subarachnoid space (1, 8, 14). Moreover, in the process of managing epileptic seizures, cognitive function alterations, and other abnormal clinical manifestations caused by POR, specialized examinations such as PET-CT, long-term video EEG monitoring, Wechsler Memory Scale, Wechsler Intelligence Scale, and the Montreal Cognitive Assessment can be utilized. Based on clinical manifestations and auxiliary examinations, a comprehensive assessment of the impact POR has on patient development, as well as the extent of potential remediation and intervention, can be summarized. On the other hand, sequence analysis via cranial MRI also facilitates further differential diagnosis with related diseases such as schizencephaly, neuroglial cyst, arachnoid cyst, and holoprosencephaly, thereby clarifying the diagnosis of POR and devising the optimal individualized treatment plan (14, 15).

Since the clinical symptoms caused by the POR depend on the location and size of the malformation, the clinical symptoms are varied, and the treatment methods vary from person to person. Ho et al. showed that the seizures caused by the POR were common, and the treatment was based on the evaluation of the temporal lobe and hippocampal structures by various MRI sequences and PET-CT, followed by 24-h video electroencephalogram monitoring, and finally, antiepileptic drug therapy and further temporal lobe epileptic resection, which showed that the treatment of epilepsy caused by the POR was effective (16). In this case, we found that the patient's initial clinical manifestation was generalized seizures, and oral antiepileptic drugs were used to control the number and duration of seizures. The 24-h video EEG after admission revealed extensive abnormalities in the left temporal lobe during the clinical seizure period, so it was difficult to choose the best surgical option to continue the symptomatic treatment with oral antiepileptic drugs.

On the other hand, the symptoms of intracranial hypertension gradually appeared in the process of development and growth, and the headache symptoms were significantly relieved after the fluid release experiment. Based on previous reports of hydrocephalus caused by POR (13, 17), combined with the patient's brain MRI showing that the porencephaly cyst communicates with the ventricular system, to alleviate the symptoms of intracranial hypertension, it was decided to perform shunt surgery for the patient. The patient's intracranial hypertension symptoms were significantly alleviated after surgery. However, the key to shunt surgery is the regulation of shunt valve pressure. Because the main feature of POR is that there is no gray matter lesion in the fissure, when the pressure is too high, it cannot achieve the effect of reducing intracranial pressure. When the pressure is too low, it will lead to tearing and bleeding of perforated malformed blood vessels, and even lead to the formation of brain herniation, and life-threatening. Therefore, for the adjustment of the shunt valve, on the one hand, the patient's clinical symptoms can be taken as one of the observation points to see whether the symptoms of the patient's intracranial hypertension headache are relieved after pressure adjustment. On the other hand, cranial CT or MRI can be used to evaluate changes in porencephaly cysts and changes in compression or exudation of peripheral brain tissue (18). For diseases such as POR and epilepsy, we not only provide individualized comprehensive treatment but also improve the quality of life of patients.