Occipital Intradiploic Encephalocoele

A 52 year old male presented with history of chronic headache and gradually enlarging swelling in occipital region of scalp.  He also complained of occasional visual disturbances in form of blurring vision. No history of seizure or trauma was noted. No history of body weakness or hemiparesis noted.

The patient was advised for Magnetic Resonance imaging (MRI). MRI shows the Cerebrospinal fluid signal intensity with T1 low, T2 high  and FLAIR suppressed in left paramedian occipital lobe. Features of volume loss of left occipital parenchyma with prominent adjacent sulci is also noted. Herniation of this lesion into the midline occipital diploic space through the defect in inner table is seen with widening of Diploic space(Figure 1A,B,C and D). Outer table is intact.

Intradiploic encephalocele is a condition characterized by the protrusion of brain tissue into the diploic space of the skull. This leads to the destruction of the inner layer of the skull bone, while the outer layer remains unaffected [1]. There is ongoing debate among experts regarding whether the term "encephalocele" accurately describes this condition, and some suggest using the term "brain herniation into the calvaria surrounding the cerebrospinal fluid [CSF]" instead [2].

Expanding skull fractures and intradiploic arachnoid cysts are comparable to intraploic encephaloceles. Although the precise causes of this ailment are unknown, it may have characteristics of a "growing skull fracture" in terms of its mechanics. Through a weakness in the dura and inner skull layer, the CSF and brain tissue may occasionally herniate into the diploic space without harming the outer layer of the skull[3]. A robust occipital muscle and pericranium protect the integrity of the outer skull layer[4].

The majority of patients with intradiploic encephaloceles exhibit seizure activity or neurological deficits, but some may experience non-specific symptoms such as headaches, dizziness, and cognitive problems. The symptoms experienced by patients can vary depending on the location of the herniation within the brain, such as if the eloquent cortex is herniated. In certain situations, patients may present with an abrupt onset of symptoms due to a sudden increase in intracranial pressure[5].

Intradiploic encephalocele is normally assessed using a combination of computed tomography [CT] and magnetic resonance imaging [MRI] scans. The herniated brain tissue within the skull defect can be seen with the aid of MRI, which provides excellent soft tissue contrast. CT scans are helpful for evaluating the bone structures and giving precise details regarding the defect in the skull [6]. MRI helps to rule out other possible differential diagnosis of bony lytic lesions which includes eosinophilic granuloma, metastasis, hemangioma, epidermoid and dermoid cyst. MRI shows the herniation of brain tissue with cerebrospinal fluid into the diploic space [7].

Repair of the dural tearing is the aim of surgery, along with decompression of the herniated cortex if incarcerated or strangulated. However surgical management for the asymptomatic incidental lesion lacks the proper evidence [8].