Neuroradiology Case of the Week

Case 33

Yevgeniy Ostrinsky, Manoj Ketkar, MD, Francisco Garcia-Morales, MD,
and P-L Westesson, MD, PhD, DDS

Clinical Presentation: Patient is a 48-year-old male presenting with right Horner’s syndrome and right-sided weakness. His symptoms progressed and within the following three days he developed non-reactive pupils and became comatose.

Radiological Findings: Upon admission, MRI of the head showed an area of restricted diffusion on the right side of the medulla, vermis, right cerebellar tonsil, and right lower paramedian portion of the cerebellar hemisphere (Fig. 1). This area demonstrated decreased ADC, suggesting acute infarction corresponding to the right posterior-inferior cerebellar artery distribution. T2-weighted image were slightly hyperintense in the right medulla and right cerebellar tonsil (Fig. 2).

Figure 1	Figure 2

   MRA of the head showed patent anterior, middle, and posterior cerebral arteries. The basilar artery and left vertebral artery were also patent, but the right vertebral artery was not visualized (Fig. 3). Neck MRA confirmed absence of signal from the right vertebral artery (Fig. 4).

Figure 3

Figure 4

   Head CT obtained three days later showed a large wedge-shaped area of low attenuation in the right cerebellar hemisphere in the right PICA territory (Fig. 5) with mass effect on the fourth ventricle and obliteration of the basal cisterns. The lateral and third ventricles were mildly dilated. In addition, there was diffuse swelling of the brain with poor grey-white differentiation and effacement of the cortical sulci (Fig. 6).

Figure 5	Figure 6

   Subsequent MRI and MRA of the brain showed the infarct in the right medulla and right cerebellar hemisphere as well as vermis (Fig. 7). The cerebellar tonsils had herniated downwards through the foramen magnum with tip approximately 2 cm below the foramen (Fig. 8).

Figure 7	Figure 8

   MRA at this time showed occlusion of the bilateral internal carotid arteries at the level of the cavernous sinus. Intra cerebral flow could not be demonstrated (Fig. 9).

Figure 9

Diagnosis: Wallenberg’s Syndrome (lateral medullary infarction) followed by herniation.

Discussion:
   Wallenberg’s syndrome is characterized by an ipsilateral Horner's syndrome and loss of pain and temperature sensation over the face on the same side, associated with contralateral loss of pain and temperature sensation in the body. Vertigo, nausea, and vomiting are usually also present, as well as limb ataxia on the side of the lesion. The ninth and tenth cranial nerves may be affected causing swallowing difficulties. The pathogenesis of this syndrome includes vertebral artery dissection, thrombosis, emboli, fibromuscular dysplasia and syphilitic arteritis.
   The lesion was traditionally attributed to a dorsolateral medullary infarction with posterior inferior cerebellar artery occlusion. However, careful studies showed that in the majority of cases the vertebral artery is involved, with or without extension to the PICA.
   Isolated PICA disease produces thin lesions leading to mild symptoms. Short-segment vertebral artery disease is associated with classic diagonal band-shaped lesions confined to the posterolateral medulla leading to classic symptoms. Both lesions are associated with atherothrombotic vascular disease. Long-segment vertebral artery disease is associated with either large MRI lesions, most likely due to dissection, or lesions similar to isolated PICA disease, usually related to atherothrombotic event. In a number of cases patients present with a normal angiogram. It is believed that these patients had a cardiac source of embolism, with subsequent recanalization at the time of angiography, producing minor fragmentary symptoms.
   The syndrome has been regarded in general as a benign condition, with slowly resolving symptoms. However, several authors reported more dismal outcomes, with mortality rates of up to 15%.

References:

1. Chiti-Batelli S, Delap T. Lateral medullary infarct presenting as acute dysphagia. Acta Otolaryngol 2001; 121: 419-420.
2. Kim JS, Lee JH, Choi CG. Patterns of lateral medullary infarction: vascular lesion-magnetic resonance imaging correlation of 34 cases. Stroke 1998 Mar;29(3):645-52.
3. Manabe Y, Murase T, Iwatsuki K, Warita H, Hayashi T, Sakai K, Abe K. Infarct presenting with a combination of Wallenberg and posterior spinal artery syndromes. J Neurol Sci. 2000 Jun 15;176(2):155-7.
4. Min WK, Kim YS, Kim JY, Park SP, Suh CK. Atherothrombotic cerebellar infarction: vascular lesion-MRI correlation of 31 cases. Stroke 1999 Nov;30(11):2376-81.