Fascicular Abducens Palsies

The anatomic neighbors of the paramedian pontine reticular formation (the PPRF, also the center for horizontal gaze control) include the facial nerve, the (uncrossed) pyramidal tracts, the sensory and sympathetic long tracts, and the abducens nerve (■ Fig. 10.7). The clustered proximity of these structures and the long intrapontine course of the sixth cranial nerve make collateral damage very common for fascicular lesions of the abducens nerve (■ Table 10.3). The classical brainstem syndromes described in the nineteenth century literature are seldom seen in isolation. The accessory or collateral symptoms associated with damage to the sixth nerve provide invaluable clues to the topographic clinical diagnosis of fascicular sixth nerve palsies. Monosymptomatic fascicular palsies are found in association with microvascular or demyelinating disorders, but are not associated with other diseases.

Fig. 10.7. Schematic section through the pons at the level of the abducens nuclei. The paths of the fascicles of the sixth and seventh cranial nerves are diagrammed to show the internal genu of the facial nerve. *Medial longitudinal fasciculus; X probable location of the sympathetic tract

Superior, medial and lateral vestibular nuclei

Inferior cerebellar peduncle

Fig. 10.7. Schematic section through the pons at the level of the abducens nuclei. The paths of the fascicles of the sixth and seventh cranial nerves are diagrammed to show the internal genu of the facial nerve. *Medial longitudinal fasciculus; X probable location of the sympathetic tract

Medial Longitudinal Fasciculus

Inferior cerebellar peduncle

Table 10.3. Brainstem syndromes with fascicular abducens pareses

Name

Affected structures

Associated brainstem signs and symptoms

Gasperini's syndrome (pontine tegmental syndrome)

PPRF, seventh nerve, (trigeminal and vestibular neurons), medial lemniscus, spinothalamic tract

Ipsilateral: gaze palsies, fifth, seventh, and eigth nerve pareses

Contralateral: sensory loss

Cestan Raymond syndrome

cerebellar peduncles; corticospinal tract; medial lemniscus

Ipsilateral: cerebellar ataxia Contralateral: hemiparesis, hemihypesthesia

Foville syndrome

Facial nerve nucleus, (trigeminal neurons, ciliospinal tract); corticospinal tract

Ipsilateral: seventh nerve paresis

(fifth nerve component), Horner's syndrome

Contralateral: hemiparesis

Millard Gubler syndrome

Facial nerve nucleus; corticospinal tract

Ipsilateral: facial palsy; Contralateral: hemiparesis

PPRF Paramedian pontine reticular formation

PPRF Paramedian pontine reticular formation

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Responses

  • niklas eichelberger
    Where is the medial longitudinal fasciculus located?
    6 years ago

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