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Case Report

An incidental finding of Dandy-Walker malformation

Hochberg, Eric MPAS, PA-C; Niles, Erin MS, PA-C

Author Information
Journal of the American Academy of Physician Assistants: January 2021 - Volume 34 - Issue 1 - p 22-24
doi: 10.1097/01.JAA.0000723916.22400.8f
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Abstract

CASE

A 41-year-old woman presented to the ED via emergency medical services in respiratory distress, with a chief complaint of 2 days of cough and shortness of breath.

History

The patient's past medical history was significant for morbid obesity, obstructive sleep apnea, hypertension, and type 2 diabetes. On arrival to the ED, she was alert, in respiratory distress, and hypotensive. Shortly after admission to the ED, she suffered a respiratory arrest requiring emergency endotracheal intubation.

IV broad-spectrum antibiotics, vasopressor support, and fluid resuscitation were initiated. Chest radiograph and laboratory values were consistent with severe acute respiratory distress syndrome (ARDS) by Berlin criteria, with bilateral patchy infiltrates on her chest radiograph and a PaO2 to FiO2 of less than 100.1 Despite interventions to optimize ventilation and oxygenation, the patient required increasing ventilator support with refractory respiratory acidosis and hypoxemia.

Due to the need for escalating support and progressive clinical decompensation, the patient was transported to our tertiary care center in critical condition.

Physical examination

On arrival, her vital signs were: heart rate 164 beats/minute; respirations 34; SpO2 46% to 88%; and BP 95/50 mm Hg with a mean arterial pressure (MAP) of 65 mm Hg on two vasopressors and an inotrope. She was afebrile. On examination, she was sedated and chemically paralyzed, pale, and tachycardic.

Diagnostic testing

Her laboratory results on arrival were significant for respiratory and metabolic acidosis with a pH of 7.17 (normal range, 7.35-7.45), a PaCO2 of 60 mm Hg (normal range, 35-45 mm Hg), and a lactate of 6.5 mmol/L (normal range 0.5-2.2 mmol/L). A complete blood cell (CBC) count revealed leukocytosis, with a white blood cell count of 15,000 cells/mm3 (normal range, 4.5-11,000 cells/mm3). A chemistry panel revealed mild hyperkalemia with a potassium of 5.5 mmol/L (normal range, 3.5-5.1 mmol/L), elevated blood urea nitrogen of 42 mg/dL (normal range, 7-17 mg/dL), and elevated creatinine of 1.3 mg/dL (normal range, 0.52-1.04 mg/dL).

Management

When conventional and rescue mechanical ventilation failed to resolve the patient's severe, persistent hypoxia and hypercarbia, she was emergently cannulated for veno-venous extracorporeal membrane oxygenation (VV ECMO). She suffered multiple cardiac arrests before and during cannulation. Following cannulation, the patient was stabilized in our dedicated VV ECMO unit. Per our unit's practices, we collected two sets of blood cultures, a urinalysis with reflex to urine culture, and urine Legionella and pneumococcal antigens. A broncheoalveolar lavage was performed and a specimen was sent for a respiratory viral panel and culture with Gram stain.

Box 1
Box 1

The patient initially underwent targeted temperature management with a goal temperature of 34° C to 36° C (93.2° F to 96.8° F) for the 48 hours after her cardiac arrest. She was weaned from sedation and vasopressor support over the next few days.2 She completed a 10-day course of empiric broad-spectrum antimicrobials, though no viral or bacteriologic cause of her respiratory failure was ever identified. The patient's pulmonary function slowly improved and she was able to be successfully decannulated from VV ECMO on hospital day 13.

Despite her pulmonary recovery, the patient's mental status remained depressed several days after discontinuing sedation. Her physical examination consistently revealed intact brainstem reflexes and withdrawal to painful stimuli only. A broad differential for her encephalopathy was developed that included metabolic derangements, toxic or medication adverse reactions, neurologic injury, or anoxic encephalopathy given her repeated cardiac arrests and prolonged hypoxia before cannulation for ECMO.

Workup for an occult infection or potential toxic or metabolic source was unrevealing, as was continuous electroencephalogram (EEG). Additionally, a CT scan of the head was pursued to identify other potential causes of her altered mental status, as about 7% of patients on VV ECMO suffer neurologic injury such as hemorrhagic or ischemic stroke, hypoperfusion due to profound hypotension, or anoxic.3 The CT revealed a cystic structure in the right posterior fossa measuring 4.5 cm by 4.5 cm and appearing to communicate with the fourth ventricle, consistent with a Dandy-Walker variant. (Figures 1 and 2). This finding, although striking on CT imaging, did not account for her encephalopathy. The patient slowly returned to her baseline neurologic status and her encephalopathy was likely multifactorial, attributed to a combination of critical illness and medication adverse reactions.

FIGURE 1.
FIGURE 1.:
Sagittal CT showing Dandy-Walker malformation: hypoplastic vermis (A), elevated tentorium (B), cystic formation of and communication with the fourth ventricle (C), and enlarged posterior fossa (D)
FIGURE 2.
FIGURE 2.:
Axial CT showing Dandy-Walker malformation (arrow)

Although the CT finding of a Dandy-Walker variant did not explain her encephalopathy, it revealed an undiagnosed congenital anomaly in a critically ill patient and warranted further investigation and multidisciplinary collaboration for follow-up. This case provided a unique opportunity to share an interesting case of a congenital abnormality previously undiagnosed in an adult.

DISCUSSION

Dandy-Walker malformation, also called Dandy-Walker complex, is a relatively rare congenital anomaly affecting the posterior fossa and occurring in 1 in 30,000 births.4 Its hallmark characteristics include hypoplasia of the vermis, dilation of the fourth ventricle, and an enlarged posterior fossa.4,5 Although the diagnosis of Dandy-Walker malformation and its variants is usually made in infancy, 10% to 20% of patients are asymptomatic and remain undiagnosed until adolescence or adulthood, as was the case with this patient.6,7

Dandy-Walker malformation and other malformations of the posterior fossa can be suggested by prenatal ultrasound findings during the basic sonographic survey of fetal anatomy, which usually occurs around 20 weeks of gestation.8 Multiplanar neurosonography may then be used to investigate these abnormal findings.9 Obtain postnatal imaging to confirm prenatal diagnosis.10

Dandy-Walker malformations are sporadic and may exist in isolation, but up to 90% are associated with other anomalies, including cardiac, gastrointestinal, orthopedic, genitourinary, and neurologic anomalies.10 Some patients may have developmental delays, with chromosomal abnormalities occurring in 50% of patients.10,11 Dandy-Walker disorders exist as a continuum that, in the most severe forms, is associated with delayed motor development and obstructive hydrocephalus. In patients without a perinatal diagnosis, Dandy-Walker malformation may be considered in patients presenting with language or motor delays, macrocephaly, seizures, or other symptoms consistent with obstructive hydrocephalus.4

Dandy-Walker variant is considered a less-severe form of Dandy-Walker malformation and is defined by classic Dandy-Walker malformation findings but with limited vermis hypoplasia. Due to the variant being less severe, patients may present with milder symptoms and the malformation may be found incidentally later in life, as in this patient.12,13 A review of 12 cases of incidental Dandy-Walker malformation discovery found preserved communication between the fourth ventricular cyst and surrounding basal cisterns may allow Dandy-Walker malformation to remain asymptomatic in these patients.11 In these patients, watchful waiting without specific treatment may be indicated if they remain asymptomatic.

Invasive treatment of Dandy-Walker malformation may include the surgical placement of a cystoloperitoneal (CP) or ventriculoperitoneal (VP) shunt or endoscopic third ventriculostomy (ETV) to relieve symptoms of obstructive hydrocephalus.4 Additional treatment may involve occupational and physical therapy to address developmental delays, or other interventions specific to the associated aneuploidies, malformations, and symptoms occurring in association with Dandy-Walker malformation.4 Patient prognosis varies based on the severity of the malformation and associated features.

Although our patient did not require any acute intervention for her diagnosis and her encephalopathy eventually resolved, her case illustrates the classic imaging findings of the Dandy-Walker variant malformation. Her case demonstrates a clinical challenge of managing Dandy-Walker malformation findings in the context of concomitant hypoxic injuries and presents a rare finding of Dandy-Walker malformation outside of the perinatal period.

CONCLUSION

Following the CT scan revealing the patient's Dandy-Walker variant, the treatment team held further discussions with the patient's parents about her past functional history. Her family stated that the patient had never experienced neurologic deficits or developmental delays, led a fairly active lifestyle, and possessed a master's degree in childhood education. They had no knowledge of the Dandy-Walker malformation or of any neuropsychiatric concerns.

The patient continued to recover and her encephalopathy started to improve in the days following her CT scan, ultimately resolving over time. On hospital day 24, she was discharged to an acute traumatic brain injury rehabilitation center and follow-up with a neuropsychologist was recommended. She was also followed by outpatient pulmonology. One year after her hospitalization, she had only a slight speech irregularity without any other neurologic deficits. She continues to do well and is followed regularly by her primary care provider and pulmonologist.

REFERENCES

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Keywords:

Dandy-Walker malformation; veno-venous extracorporeal membrane oxygenation; congenital; altered mental status; encephalopathy; respiratory distress

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