Point 5 Intro Pathway Deficit Note Summary Overview Problems Contents Anatomy

YOU DO NOT HAVE TO READ THE BOXED IN AREA IF YOU DO NOT WANT TO This is due to TWO DECUSSATIONS of pathways involved in conveying cerebellar information to the spinal cord. To understand all of this, let's start at the LEFT accessory cuneate nucleus, which you now know receives information from the LEFT side of the upper extremity. Cells in the LEFT accessory cuneate nucleus possess axons that comprise the LEFT cuneocerebellar tract and synapse on cells in the LEFT cerebellar cortex called granule cells. The axons of granule cells synapse on Purkinje cells. Purkinje cell axons synapse on cells in the deep white matter of the cerebellum called DEEP CEREBELLAR NUCLEI. There are four of these deep cerebellar nuclei on each side of the cerebellum. They are called fastigial, globose, emboliform and dentate. We will NOT worry about these nuclei too much at this time, but we need to know that they contain cells whose axons LEAVE the cerebellum (efferent; exit) in a large bundle called the SUPERIOR CEREBELLAR PEDUNCLE (Point #17). The superior cerebellar peduncle courses rostrally and CROSSES in the caudal midbrain (decussation #1). After crossing, axons synapse in the RED NUCLEUS (midbrain; we will discuss later in POINT #21; don't worry about it at this time) and in the ventral lateral (VL) and ventral anterior (VA) nuclei of the thalamus. Cells in VL and VA project to the motor cortex, which of course contains the cells of origin of the CORTICOSPINAL TRACT. As you know, the corticospinal tract CROSSES in the caudal medulla (decussation #2) and innervates spinal cord neurons.