Term
| Damage to One Occulomotor Nerve |
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Definition
Lateral Strabismus - Ipsalateral eye deviates laterally (paralyzed medial rectus and unnopposed lateral rectus) "down and out." Results in diplopia.
Ipsalateral ptosis - levator palpebrae superioris paralyzed.
Mydriasis - Ipsalateral pupil dilation (unopposed dilator pupillae).
Lens cannot focus for near vision
Bad - usually indicative of compression on nerve from brain herniation. |
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Term
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Definition
| Medial Strabismus - Reciprocal of lateral strabismus, now there is an unopposed medial rectus. Note if the nucleus is damaged rather than the nerve, the ipsalateral eye will not be able to abduct past mid-position and the contralateral eye will not adduct past mid-position - lateral gaze paralysis (the nucleus contain internuclear interneurons which cross after leaving the abducens nucleus to the contralateral MLF and synapse on medial rectus motor neurons in the occulomotor nucleus. Often seen with increased cranial pressure. |
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Term
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Definition
| Internuclear Opthalmoplegia. Removes excitatory influence of medial rectus so that the eye ipsalateral to the lesion fails to move medially past midposition. It still functions when used without the opposite lateral rectus. |
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Term
| Damage to Area Surrounding Abducens Nerve |
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Definition
| One-and-a-half: Inability of patient to move either eye to the side of the lesion in lateral gaze, or to move the eye on the side of the lesion in gaze toward the opposite side e.g. only right eye moves in a left lesion. |
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Term
| Damage to Hypoglossal Nerve |
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Definition
| Weakness of one side of the tongue. Also, lower motor lesion, so atrophy as well. Tongue deviates towards side of the lesion |
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Term
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Definition
| When trigeminal fibers ending in the cervical cord overlap spinal fibers that represent adjacent areas of skin around mouth (more caudal lesion of trigeminal = better prognosis). Sensory loss from the spinal cord will begin at the back of the head and converges at the mouth. |
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Term
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Definition
| Brief attacks of excruciating pain, usually less than one minute in duration in the trigeminal nerve. No abnormalities between attacks. Usually caused by compression of a blood vessel or tumor. |
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Term
| Damage to Facial Motor Nucleus/Facial Nerve |
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Definition
| Lower motor neurons of each facial motor nucleus (muscles of facial expression) project to the ipsalateral muscles so damage to this nucleus or to the facial nerve causes weakness on the ipsalateral half. Corticalbulbar projections to the motor neurons for muscles below the eye are predominately crossed. So a patient with a stroke may have lower left facial weakness if the right side of the brain was affected, but can raise both eyebrows. |
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Term
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Definition
Afferent: CNII
Efferent: CNIII for constriction (parasympathetic), Sympathetic chain for dilation |
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Term
| Miosis (and mild ptosis) caused by? |
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Definition
Sympathetic disruption
Path is from hypothalamus->Brainstem->T1/T2->sympathetic chain->internal carotid->ophthalmic artery. Lesion anywhere here can cause miosis and mild ptosis (tarsal muscles). Ptosis defined as any part of iris covered. CNIII lesions, on the other hand, cause complete ptosis. |
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Term
| Midbrain lesions typically result in? |
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Definition
| Midposition to large pupils often non-reactive (fixed). Usually due to stroke/compression. |
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Term
| Pontine lesions usually result in? |
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Definition
| True pinpoint pupils due to loss of sympathetic innervation and increased parasympathetic activity. Usually from a pontine hemmorrhage. |
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Term
| Tectal lesions usually result in? |
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Definition
| Large, fixed pupils that may be irregular. Often from severe downward herniation. |
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Term
| What are the signs of Horner's syndrome? |
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Definition
| Unilateral loss of sympathetic efferents in brainstem or peripherally results in miosis, ptosis, anhydrosis, and enopthalmos. |
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Term
| Trochlear lesion results in what? |
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Definition
| Vertical diploplia when patient looks medially with the affected eye. Possible head tilt. |
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Term
| Internuclear ophthalmoplegia |
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Definition
| Caused by unilateral or bilateral lesion of the MLF. During lateral gaze, the eye ipsalateral to the damaged MLF (the ADducting eye) doesn't cross the midline, while the other eye (the ABducting eye develops nystagmus. Often seen with MS. |
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Term
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Definition
| Unconscious patient reflex (Doll's eye, Oculocephalic reflex). Turning the head one way will cause eyes to move conjugately in the opposite direction. Eyes fixed to point in space. In a patient with a brainstem lesion, the eyes will remain fixed in the head (and not at a point in space). |
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Term
| Vestibulo-Ocular Reflex (cold caloric). |
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Definition
| Uncoscious reflex (Cold Caloric Response). Based on intact vestibular function. Ice water into the ear of an unconscious patient with an intact brain stem will cause both eyes to move conjugately to the irrigated side (decreased rate of vestibular afferent firing). Warm water will do the opposite. With an intact cortex, nystagmus away from the irrigated side will occur. With an MLF lesion, only the ipsilateral eye moves toward the stimulis. |
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Term
| A lesion to the medulla can cause (trigeminal involvement)? |
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Definition
| Loss of pain and temp on the ipsalateral face by damage to the trigeminothalamic tract. (An extension of the spinothalamic tract that has crossed over again in the cervical spinal cord). SO LESIONS ABOVE CERVICAL SPINAL CORD AFFECT IPSALATERAL PAIN AND TEMPERATURE WHILE THOSE BELOW (IN THE SPINOTHALAMIC TRACT) AFFECT CONTRALLATERAL PAIN AND TEMPERATURE. |
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Term
| Sign of a motor lesion to CNV? |
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Definition
| Jaw deviates toward weak side. |
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Term
| Trigeminal neuralgia (tix douloureux) |
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Definition
| Paroxysmal attacks of severe facial pain. Can be disabling. Often a trigger zone. |
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Term
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Definition
| Pain in V1 associated with CNVI palsy from inflammation of the petrous apex. |
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Term
| Lower half of the face gets bilateral, ipsalateral or contralateral innervation? Upper face? What is the effect of a super nuclear lesion? |
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Definition
| Only contralateral (like other muscles of body). Upper one third gets bilateral innervation. Supranuclear lesions do not affect the forehead. |
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Term
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Definition
| Cortical stroke will cause contralateral lower facial weakness. |
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Term
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Definition
| Peripheral lesion of CNVII. May have hyperacusis or loss of taste depending on position. In a peripheral (lower motor) lesion, all innervation to the muscles of the ipsalateral face will be affected (left CNVII lesion means no forehead or lower face innervation on the left side). |
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Term
| Crocodile tears (synkinesis) |
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Definition
| Aberrant regeneration of CNVII |
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Term
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Definition
Midbrain lesion. Contralateral to lesion: hemiparesis, hyperreflexia, depressed muscle tone, Babinski sign, spasticity. From descending corticospinal tracts in cerebral peduncles.
Ipsalateral to lesion: Lateral eye deviation, pupil dilation, severe ptosis, inability to look up, down, or medially. From CNIII palsy. |
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Term
| Parinaud's Syndrome (dorsal) |
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Definition
Midbrain lesion. Paralysis of upgaze "setting sun sign"
Light-near dissociation. |
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Term
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Definition
Pontine Lesion
Ipsalateral CNVI and CNVII palsy (peripheral)
Contralateral hemiparesis (descending CST). |
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Term
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Definition
Pontine lesion:
Millard-Gubler Syndrome (Ipsalateral CNVI and VII palsy -peripharal; contralateral hemiparesis) and Contralateral loss of proprioception and vibration (medial lemniscus). INO. |
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Term
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Definition
Pontine lesion:
Usually seen after pontine stroke or hemorrhage. Near total transection of brainstem. RAS intact. All afferent and efferent tracts destroyed including corticobulbar. In worst case only CNIII functions. |
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Term
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Definition
Medullary Lesion:
Caused by a lateral medullary infarct from PICA. Contralateral loss of pain and temp from spinothalamic lesion. Horner's syndrome from loss of DESCENDING sympathetics (loop all the way back up from T1/T2). Ipsilateral loss of facial sensation (descending sensory nucleus of CNV). Lesions of CNIX and CNX cause dysphagia and dysarthria. Ipsalateral dysmetria and ataxia (Inferior cerebellar peduncle). |
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Term
| What does the MLF connect? |
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Definition
| The Paramedian Pontine Reticular Formation (PPRF) -abducens nucleus complex of the contralateral side to the oculomotor nucleus of the ipsilateral side. |
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