The PICA syndrome is also known as "lateral medullary syndrome", or "Wallenberg's syndrome", after Wallenberg's description in 1895. This is the most common brainstem stroke. It is typified by vertigo, ipsilateral hemiataxia, dysarthria, ptosis and miosis. Most patients with this stroke recover very well and often resume their previous activities (Nelles et al, 1998). Patients often have a Horner's syndrome (unilateral ptosis, miosis and facial anhidrosis).
There also may be saccadic dysmetria (overshoot), saccadic pulsion (pulling of the eye during vertical saccades toward the side of lesion -- called ipsipulsion). Rarely, the eyes go towards the opposite side of the lesion (called contrapulsion). (Kaski et al, 2012). Because the eyes can go either way, ipsi or contra, the localizing significance of pulsion is not teriffic.
Prognosis is generally quite good with full or near full recovery expected at 6 months. Diagnosis is generally via MRI (see below). CT-angiography with 3D reconstruction has gotten good enough in recent years to be helpful too.
ABR testing is often abnormal in persons with central Horner's syndrome (Faught and Oh, 1985), but as the lesion in Wallenberg syndrome is usually below the auditory connections, Horners due to Wallenbergs are not generally associated with abnormal ABR.
PICA may arise from the vertebral artery (the usual case), or as a separate branch of the basilar artery. Because of the far more common origin from the vertebral artery, most "PICA" syndrome strokes actually are due to vertebral artery occlusion (Kim 2003). Cardiac embolism causes only 5% of these strokes, while dissection causes 15% (Kim, 2003).
PICA is the most common site of occlusion from propagating thrombus or embolism caused by injury to the third section of the vertebral artery, and Wallenberg's syndrome is the most common stroke caused by chiropractic manipulation (Caplan, 1986).
Caplan LR. Vertebrobasilar disease. In Barnet HJM (and others, Eds), Stroke: Pathophysiology, Diagnosis and Management. New York: Chrchill-Livingstone, pp 549-619, 1986
Faught E, Oh SJ. Brainstem auditory responses in brainstem infarction. Stroke 1985. 16:701-705
Kaski, D., et al. (2012). "Up-down asymmetry of saccadic contrapulsion in lateral medullary syndrome." J Neuroophthalmol 32(3): 224-226.
Kim JS (2003). "Pure lateral medullary infarction: clinical-radiological correlation of 130 acute, consecutive patients." Brain 126(Pt 8): 1864-72.
Nelles G, and others. Recovery following lateral medullary infarction. Neurology 1998:50:1418-1422
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