AN59.1-4 | Pons — Glossary

Ventral portion of the pons containing corticospinal fibres scattered among pontine nuclei and transverse pontocerebellar fibres

Dorsal portion of the pons containing cranial nerve nuclei (V-VIII), MLF, reticular formation, and ascending tracts

Rounded elevation on the 4th ventricle floor caused by CN VII fibres looping over the CN VI nucleus

MLF — fibre bundle near the midline connecting CN VI to contralateral CN III for conjugate horizontal eye movements

INO — MLF lesion causing impaired adduction on horizontal gaze with abduction nystagmus in the contralateral eye; bilateral INO diagnostic of MS

Bilateral basis pontis destruction causing quadriplegia and anarthria with preserved consciousness and vertical eye movements

Unilateral lower pons lesion causing ipsilateral CN VI and VII palsy with contralateral hemiplegia

Brachium pontis — largest cerebellar peduncle carrying corticopontocerebellar input from the contralateral cerebral cortex via pontine nuclei

Pigmented noradrenergic nucleus in the upper pons; main source of norepinephrine in the CNS; involved in attention, arousal, and mood

Acute idiopathic LMN facial nerve palsy affecting the entire ipsilateral face; most common cause of facial palsy in India

Protective reflex: afferent CN V1 (corneal sensation) → efferent CN VII (bilateral orbicularis oculi contraction/blink)

GVE parasympathetic nucleus of CN VII controlling submandibular, sublingual, and lacrimal gland secretion

Branch of CN VII carrying taste from the anterior 2/3 of the tongue and parasympathetic fibres to the submandibular and sublingual glands

Junction of the pons, medulla, and cerebellum; site of acoustic neuromas (vestibular schwannomas) affecting CN VII and VIII

Vestibular schwannoma — benign tumour at the cerebellopontine angle causing progressive unilateral hearing loss, tinnitus, and facial weakness

Tic douloureux — severe lancinating facial pain in the distribution of CN V (usually V2/V3); often caused by vascular compression of the nerve root

VOR — reflex mediated via vestibular nuclei and MLF that stabilises gaze during head movement by producing compensatory eye movements

Longitudinal groove on the 4th ventricle floor separating the medial motor (efferent) area from the lateral sensory (afferent) area

Paramedian pontine reticular formation — horizontal gaze centre adjacent to CN VI nucleus coordinating conjugate horizontal eye movements

Hypertensive bleed into the pons; pinpoint pupils are pathognomonic; high mortality; may cause locked-in syndrome

Decussation of auditory fibres in the pons; most cochlear nucleus fibres cross here, explaining why unilateral cortical lesions do not cause deafness