Regional Anatomy of PICA:
The posterior inferior cerebellar artery also known as PICA is the largest branch of the vertebral artery, passes on an irregular course between Medulla and Cerebellum. It is one of the 3 major arteries supplying the cerebellum. It supplies the posterior part of inferior surface of Vermis, Central nucleii of Cerebellum and undersurface of Cerebellar hemisphere.It also supplies Medulla ( branches of PICA along with medullary branches of Vertebral artery) and Choroid Plexus of 4 th ventricle.
Adolf Wallenberg (November 10, 1862-1949) ,a German internist and neurologist, first described the clinical manifestations (1895) and the autopsy findings (1901) in occlusions of the arteria cerebelli posterior inferior (Wallenberg syndrome)
- It results from thrombosis of Posterior Inferior Cerebellar Artery.
- Causing lateral part of the medulla oblongata to infarct.
- The most commonly affected artery is the vertebral artery, followed by the PICA, superior middle and inferior medullary arteries.
Signs and Symptoms that are Characteristic of Wallenberg Syndrome are-
- Dysphagia and Dysarthria ( Due to paralysis of Ipsilateral palatal and laryngeal muscles- Innervated by Nucleus Ambiguus)
- Analgesia and Thermaesthesia on the Ispsilateral side of the face ( Due to lesion of Nucleus and Spinal tract of Trigeminal nerve)
- Vertigo, Nausea, Vomiting and Nystagmus. ( Lesion of Vestibular nucleii)
- Ipsilateral Horner Syndrome ( due to lesion of Descending Sympathetic fibres) Mnemonic- “Horny PAMELa” for Ptosis, Anhydrosis, Miosis, Enophthalmos and Loss of ciliospinal reflex
- Cerebellar Symptoms and Signs-
- Cerebellar Ataxic/ Drunken Gait
- Dysdiadochokinesia ( unable to perform quick alternative repeated actions like pronation/supination)
- Pendular knee jerk
- Intention Tremor ( Tremor increases as fingers arrive the target)
- Rebound phenomenon
- Scanning speech
In Lateral Medullary Syndrome following structures are affected-
- Nucleus Ambiguus
- Nucleus Solitarius
- Vestibular Nucleus
- Cochlear Nucleus
- Spinocerebellar tracts
- Lateral Spinothalmic tract
- Spinal Nucleus of Trigeminal Nerve
- Tract of Trigeminal Nerve
“The Only way not to miss the Diagnosis is to keep PICA syndrome in mind, then you can head for confirmation”