Basal Encephalocele Presenting with Bitemporal Hemianopsia in an Adult Male

ABSTRACT

Basal encephaloceles are uncommon malformations that are usually congenital in nature, although, occasionally, they can be traumatic. When they are congenital, they are associated with skull and facial midline defects, central nervous system abnormalities, and possible ocular and visual problems. The authors present a case of an adult male with a basal encephalocele who presented with a bitemporal hemianopsia. Ocular abnormalities, visual loss, and visual field deficits have previously been reported in patients with basal encephalocele; however, there does not appear to be any reported cases with formal visual field testing to demonstrate specific defects such as a bitemporal hemianopsia.

Case report

A 66-year-old male was involved in an automobile accident and subsequently complained of bitemporal visual field loss, confusion, and personality changes. There was no clear history of head trauma in the accident. His past medical history was significant for a cleft palate that was surgically repaired as a child, as well as the absence of a nasal septum, which was repaired at the age of 16 years old.

He was initially seen in another city where a magnetic resonance imaging (MRI) of the head was grossly abnormal and suggested a possible pituitary mass and hydrocephalus. The patient was evaluated for hydrocephalus, including lumbar punctures with normal opening pressures. Following the lumbar punctures, the patient reported a subjective improvement in his peripheral vision, although this was not reflected in repeat automated visual field testing. This symptomatic improvement prompted a neurosurgeon to place a ventriculoperitoneal shunt for treatment of presumed normal pressure hydrocephalus.

The patient was then seen locally by a neurosurgeon who diagnosed him with a basal encephalocele. Since the patient continued to have visual field complaints, he was referred to our neuro-ophthalmic service for evaluation. On our initial examination, best-corrected visual acuities were 20/25 in the right eye and 20/30 in the left eye. External examination showed ptosis of the right upper eyelid and ocular hypertelorism (Figure 1).

Figure 1.

External photograph demonstrating ocular hypertelorism.

The anterior segment examination showed bilateral nuclear sclerotic cataracts but was otherwise unremarkable. The posterior examination showed a cup-to-disc ratio of 0.5 in the right eye and 0.6 in the left eye. The nerves were flat in appearance without pallor, haemorrhages, or oedema. The remainder of the posterior examination was unremarkable bilaterally. Further evaluation included a Humphrey visual field 30-2 SITA-Fast (Figure 2), which showed a bitemporal hemianopsia with good reliability. These visual fields were compared with previous Humphrey visual fields done approximately 19 months earlier and found not to have changed significantly.

Figure 2.

Humphrey visual field 30-2 SITA-Fast.

Repeat MRI of the head was performed at our institution (Figures 3 and 4) and confirmed a broad sphenoethmoidal basal encephalocele. According to the radiologic report, the encephalocele contained brain tissue as well as optic nerve sheath complexes, infundibulum, and pituitary tissue. Its maximum dimensions measured 4.0 cm in the anterior-posterior axis, 3.0 cm in the craniocaudal axis, and 2.3 cm in the transverse dimension. The MRI also showed agenesis of the corpus callosum, radiologic evidence of ocular hypertelorism, and the previously placed ventriculostomy catheter.

Figure 3.

T1-weighted MRI of the head, sagittal view.

Figure 4.

T2-weighted MRI of the head, coronal views, demonstrating the relationship of the basal encephalocele to the optic chiasm.

Discussion

Encephaloceles are congenital malformations resulting in herniation of meningeal and brain tissue through a skull defect, which can be classified as posterior (occipital) or anterior (frontal or basal). Basal encephaloceles are the least common of these three types and are further subdivided according to the location of the defect, including sphenopharyngeal, spheno-orbital, sphenomaxillary, sphenoethmoidal, and transethmoidal.¹

Basal encephaloceles are malformations due to failure of the anterior neural tube to close between days 25 and 27 of gestation. They may be associated with other midline abnormalities, including cleft palate, ocular hypertelorism, and craniosynostoses. Presenting symptoms may also include cerebrospinal fluid (CSF) rhinorrhoea, endocrine abnormalities, recurrent meningitis, or vision changes.^1–4 Hydrocephalus is also seen in association with these defects.⁵ Congenital encephaloceles are most commonly diagnosed during childhood due to their association with other midline defects or the presence of CSF rhinorrhoea or recurrent meningitis. Less commonly, these encephaloceles may go undiagnosed until adulthood.

Associated ocular abnormalities seen with basal encephaloceles besides visual loss and hypertelorism include cataract,² optic atrophy,¹ optic disc dysplasia (including morning glory disc anomaly),⁶ optic disc pits with maculopathy,⁷ chorioretinal atrophy and colobomas,¹ strabismus,⁸ and nsytagmus.²

This case demonstrates a patient with a sphenoethmoidal encephalocele who presented with a bitemporal hemianopsia and provides the automated visual field testing showing the deficit. His medical history includes a cleft palate and absent nasal septum that were both repaired as a child, as well as ocular hypertelorism and right upper eyelid ptosis. In this particular case, it is unknown if the right upper eyelid ptosis is related to the basal encephalocele or an incidental finding that is unrelated. The mechanism of the bitemporal hemianopsia is compression of the optic chiasm by the encephalocele, which can be seen in the MRI coronal views (Figure 4).

The facial and midline features in this patient are highly suggestive of the encephalocele being congenital in nature, rather than traumatic. Basal encephaloceles of this type should be considered in the differential diagnosis of bitemporal hemianopsia, particularly when there are facial or midline abnormalities present.

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the article.