Images below require Macromedia's Flash Player to view

Neuroradiology Case of the Week

Case 259

B. Keegan Markhardt, MD, P-L Westesson, MD, PhD, DDS,
and Sven Ekholm, MD, PhD

Clinical Presentation: Patient is a neonate born at 41 weeks 2 days gestation by emergent cesarean section after failed vacuum extraction. APGAR was 2 at 1 minutes, 2 at 5 minutes, 3 at 10 minutes.  At delivery baby was floppy, pale and without respiratory effort, and with a cord pH 7.13 and pCO2 35.  After intubation and positive pressure support the neonate began spontaneous respiratory effort at 16 minutes.  APGAR was 6 at 20 minutes.

Diagnosis: Hypoxic ischemic encephalopathy (day 8) and multicystic encephalopathy (day 35)

Discussion: This case illustrates progression of hypoxic-ischemic encephalomalacia to multicystic encephalopathy. For another case of HIE please see our Neuroradiology Case of the Week #201.
     Hypoxic-ischemic encephalopathy (HIE) occurs in up to 0.2% of live births and is a result of ischemic insult to the brain [1]. HIE is one of the most common causes of cerebral palsy and other severe neurologic deficits in children [2]. Diffusion-weighted imaging is the most sensitive MR sequence to evaluate HIE and typically demonstrates areas of restricted diffusion suggestive of ischemia in affected areas. Apparent diffusion coefficient maps created from diffusion-weighted sequences are more sensitive for the detection of cytotoxic edema between 24 hours to 8 days of life [1]. However, they do not correlate well with the extent of ischemic injury and are not predictive of adverse outcome [2].
     Mild to moderate ischemic insult affects different areas of the preterm neonate brain than of the term neonate brain [1, 2]. In preterm neonates, the most common location for ischemic injury is to the periventricular white matter, often resulting in periventricular leukomalacia. In term neonates, cerebral blood flow redistribution preserves deep brain structures [1]. Moreover, intervascular watershed zones between the anterior and middle cerebral arteries and between the middle and posterior cerebral arteries are most affected. Both the cortex and the underlying subcortical white matter in the parasagittal locations may demonstrate restricted diffusion [2].
     Patterns of severe ischemic insult to the preterm and term neonate are more similar. In both cases, areas with high metabolic demand are injured. In the preterm neonate, ischemic injury to the brainstem, thalamus and cerebellum are more common [1, 2]. In the term neonate, ischemic injury to the lateral thalamus, brainstem the deep gray matter, posterior mesencephalon (corticospinal tracts), hippocampi and peri-Rolandic cortex (sensorimotor cortex) are more common [1, 2].
     Multiple cystic encephalomalacia (MCE) is a condition where the brain parenchyma is reduced to cysts of varying sizes. Prognosis of MCE is universally poor. MCE may follow a variety of insults to the central nervous system including asphyxia, meningitis, encephalitis and twin-to-twin transfusion [3]. The common factor linking these disparate conditions appears to be brain hypoxia. Sie et al. (2000) studied 104 children with evidence of bilateral post-hypoxic-ischemic brain damage and found that the type of hypoxia-ischemia, rather than the post-conception age at occurrence determines the pattern of brain injury [4]. In their study, multicystic encephalopathy occurred in 10 infants.
     Of the TORCH infections, congenital herpes virus infection may cause a cystic encephalopathy that closely resembles ischemic related MCE, see Neuroradiology Case of the Week #159. Congenital herpes virus is therefore a major differential diagnostic consideration for MCE. Weidenheim et al. (1995) looked at seven cases of MCE and found that six of them where secondary to HIE and one was secondary to herpes virus [5].

References:

1. Osborn AG, et al. “HIE, TERM” in Diagnostic Imaging: Brain. Amirsys 2004; Section I4, page 72-75.
2. Chao CP, Zaleski CG, Patton AC. Neonatal hypoxic-ischemic encephalopathy: multimodality imaging findings. Radiographics. 2006 Oct;26 Suppl 1:S159-72. [Medline]
3. Stannard M, Jimenez J. Sonographic recognition of multiple cystic encephalomalacia. AJR Am J Roentgenol. 1983 Dec;141(6):1321-4. [Medline]
4. Sie LT, van der Knaap MS, Oosting J, de Vries LS, Lafeber HN, Valk J. MR patterns of hypoxic-ischemic brain damage after prenatal, perinatal or postnatal asphyxia. Neuropediatrics. 2000 Jun;31(3):128-36. [Medline]
5. Weidenheim KM, Bodhireddy SR, Nuovo GJ, Nelson SJ, Dickson DW. Multicystic encephalopathy: review of eight cases with etiologic considerations. J Neuropathol Exp Neurol. 1995 Mar;54(2):268-75. [Medline]