Case of Atypical Dandy–Walker Variant in Adult with Refractory Headaches

Sir, Dandy–Walker Syndrome (DWS) is a group of anatomic and embryologic disorders characterized by failed or hypoplastic development of the midline cerebellum and a posterior fossa cyst that communicates with the fourth ventricle. Typically, DWS is diagnosed within the first year of life, often with diagnostic findings on prenatal ultrasounds.[1] DWS is rarely diagnosed in adults. Symptoms in adults vary from asymptomatic to having headaches, gait instability, or brainstem infarcts.[2–5] Imaging findings in reported adult cases have demonstrated classic features of posterior fossa cysts with rotated, hypoplastic cerebellar vermis. Treatment measures ranged from conservative measures to posterior fossa decompression.[2–5] We present an interesting case of an adult patient with refractory headaches found to have DWV with atypical features on brain imaging. The patient is a 56-year-old female with a history of hyperlipidemia, hypertension, and Peter’s anomaly of the left eye, who presented with a 3-month history of headaches and gait instability. The headaches gradually crescendoed to a 10/10 in intensity, causing her to present to the Emergency Department. The headaches were described as a constant frontal and retroorbital pressure-like pain that intensified with position changes and was associated with unsteadiness, blurred vision, and urinary urgency. The patient also stated that she had begun to feel increasingly unsteady on her feet, as if she were “standing on a boat.” She was also starting to have urinary incontinence and increasing difficulty with memory and concentration. On examination, the patient was well appearing, with wide-set eyes and alopecia. On the Montreal Cognitive Assessment, she scored a 28/30. Her cranial nerve exam was unremarkable, revealing a normal fundoscopic exam, normal eye movements, and normal pupillary reflex. Her motor and sensory exams were also unremarkable. Her reflexes revealed a 3+ left patellar reflex and positive left Hoffman’s reflex. She had subtle left-sided dysmetria on finger to nose and a positive Romberg sign. Her gait was wide-based, slow and unsteady with short stride and a multi-step turn. Differential diagnosis for a patient with positional headache, gait instability, and urinary symptoms included normal pressure hydrocephalus, idiopathic intracranial hyper tesion, communicating hydrocephalus, noncommunicating hydrocephalus, and DWS. A brain MRI was done, revealing an enlarged cisterna magna and fourth ventricle in communication with a dilated aqueduct of Sylvius, superior displacement of the cerebellar vermis, and moderate hydrocephalus with distension of optic nerve sheaths. There was an additional finding of a craniocervical junction web possibly contributing to hydrocephalus [Figure 1]. Her imaging was most consistent with DWV, but interestingly, her cerebellar vermis was well developed, unlike classic examples of DWM or DWV.Figure 1: Pre-operative T2-Weighted Brain MRI (a) Sagittal T2-weighted image demonstrating communicating hydrocephalus and presence of well-developed cerebellar vermis. (b) Axial T2-weighted image demonstrating communicating hydrocephalus. (c) Sagittal T2-weighted image demonstrating communicating hydrocephalus despite presence of scar/web (arrow) at the craniocervical junctionThe patient was started on Acetazolamide (500 mg BID) and later on Topiramate (25 mg QHS). Initially, she had some benefit, but the symptoms gradually worsened. A large-volume lumbar puncture revealed a mildly elevated opening pressure of 22 cm of water, and a marked improvement in her gait velocity and stride length post-lumbar puncture. Cerebrospinal fluid studies were unremarkable. She ultimately had a ventriculoperitoneal (VP) shunt placed (Certas plus [Codman] flow-limited, programmable valve; Initial setting was 5, allowing opening at 145 mmgH20). Three months post-operatively, she had complete resolution of her headaches and gait instability, and mild residual difficulties with concentration. Her repeat imaging at 4 months post-operatively showed successful decompression of hydrocephalus [Figure 2]. Although this imaging showed persistent, albeit significantly improved, asymmetric ventriculomegaly, clinically she had stable resolution of her symptoms.Figure 2: Post-operative Brain CT: Post-operative CT scan demonstrating resolution of cystic dilation of the fourth ventricle, appropriate expansion of well-developed cerebellum parenchyma and improvement in hydrocephalusDWS is a global developmental defect of the roof of the rhombencephalon causing the formation of a posterior fossa cyst and variable hypoplasia of the cerebellar vermis. Variants arise either due to failure of the vermis to cover the fourth ventricle or because of variable fourth ventricle foramina fenestration. DWS often has failure of both of these processes, leading to compression and elevation of the vermis.[6] The cause of DWS is variable; it can be isolated or associated with other genetic abnormalities or infections.[6] Recent genome-wide sequencing studies have also found some monogenetic causes of DWS.[7] Common variants of DWS include DWM, DWV, and Persistent Blake’s Pouch. DWM is a cystic outgrowth of the fourth ventricle, associated with hydrocephalus, complete or partial agenesis of the cerebellar vermis and, importantly, an enlarged posterior fossa with upward displacement of the tentorium, torcula and sinuses.[8] DWV is characterized by a smaller fourth ventricular cyst without enlargement of the posterior fossa or displacement of the tentorium and torcula, but still with a hypoplastic, superior-anterior rotated vermis. There is a variable degree of hydrocephalus with DMV. Persistent Blake’s Pouch is an outpouching of the superior medullary velum into the cisterna magna without communication with other subarachnoid spaces and without dysgenesis of the superior vermis or cerebellar hemispheres. Similar cystic posterior fossa malformations include a mega cisterna magna and posterior fossa arachnoid cysts. A mega cisterna magna is an expansion of the subarachnoid space into the cisterna magna, but unlike DWM, there are minimal abnormalities or rotation of the cerebellum and no associated hydrocephalus.[9] An arachnoid cyst is an isolated cyst in the subarachnoid space that does not communicate with other subarachnoid spaces, unlike DWM.[10] The case presented here is particularly interesting because the imaging findings are unusual. The imaging findings are most consistent with DMV, demonstrating cystic dilation of the fourth ventricle with communicating hydrocephalus, superior rotation of the cerebellar vermis, normal posterior fossa size, and normal positioning of the tentorium, torcula and sinuses. However, unlike typical DWV, in this case, the cerebellar architecture is completely intact, without signs of vermian hypoplasia. In addition, DWV presenting in adulthood in a person who is previously asymptomatic is itself a rare occurrence, with few previous recent reports in the literature.[2–5] Conservative management and surgical arachnoid adhesiolysis, endoscopic third ventriculostomy, and posterior fossa decompression have been utilized in these described case reports.[2–5] It is not clear why this patient decompensated with symptomatic hydrocephalus so late in life, but it is possible that the webbing noted at the cranio-cervical junction contributed by exacerbating the hydrocephalus and causing the emergence of symptoms. In summary, this is a unique case of DWV presenting in adulthood. It is particularly unusual because the imaging revealed a well-developed cerebellar vermis, but was otherwise consistent with DWV. This suggests that the imaging features associated with DWV may need to be more broadly defined. List of abbreviations DWS: Dandy–Walker Syndrome DWM: Dandy–Walker Malformation DWV: Dandy–Walker Variant BID: Twice a day QHS: Once a night Consent for publication The patient of this case report consented to the use of her imaging and history findings in publication of this manuscript. Written informed consent was obtained, and a copy of the consent form is available upon request from the editorial board. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.

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