Fisher’s Eight-And-A-Half Syndrome Related to a Dorsomedial Pontine Hematoma at CHU Campus De Lomé (Togo)

Fisher’s eight-and-a-half syndrome is a rare clinical entity characterized by the association of one-and-a-half Fisher syndrome (internuclear ophthalmoplegia (INO), gaze laterality palsy) [1] and peripheral facial paralysis, PFP (1^1/2 + 7 = 8^1/2) [2]. The anatomical structures affected are the abducens nerve nucleus, the median longitudinal fasciculus (MLF) in the pontic reticular formation and the facial nerve. The common causes of this syndrome are multiple sclerosis [3, 4], stroke [5-8] and tumors [9, 10]. We report a case of a 42-year-old female patient presenting with Fisher’s eight-and-a-half syndrome related to a dorsomedial pontine hematoma at CHU Campus de Lomé (Togo).

A 42-year-old, right-handed patient with a history of hypertension 10 years previously, poorly monitored, was admitted in april 2022 for the sudden onset of rotatory vertigo associated with rightward deviation of the mouth and visual blur evolving two days before admission. There was no history of headache, vomiting or eizure. Clinical examination revealed grade III hypertension, binocular diplopia, left PFP with a positive Charles Bell sign, right INO (paralysis of left eye adduction with preserved convergence, nystagmus of the right eye in abduction) and left gaze laterality paralysis (paralysis of left eye abduction and right eye adduction), resulting in Fisher’s eight-and-a-half syndrome (Figure 1).

The rest of the physical examination was unremarkable. A cerebral CT scan (Figure 2) performed on the third day of onset of the neurological deficit showed a spontaneous left paramedian posterior pontine hyperdensity approximately four millimeters in diameter, with no mass effect or ventricular effraction. Antihypertensive treatment and facial physiotherapy were instituted. The patient did not benefit from orthoptic rehabilitation. The evolution was favourable and the patient returned home after a week’s hospitalization with her blood pressure controlled at 130/80 mm Hg and the rest of the clinical picture unchanged. A sixmonth follow-up clinical examination showed BP at 140/100 mm Hg; normal oculomotor examination; complete regression of PFP; preservation of autonomy with a modified Rankin score of 0/6.

Fisher’s eight-and-a-half syndrome is a fairly rare clinical entity with very few documented cases, first reported by Eggenberger et al [2] in 1998. Our patient presented with right OIN, left lateralis palsy and left PFP. The paralysis of laterality of gaze to the left was manifested by an abduction deficit in the left eye and an adduction paralysis in the right eye. It is due to nuclear damage to the left VI^th cranial nucleus, which controls the homolateral lateral rectus and projects to the contralateral IIIrd cranial nucleus via the medial longitudinal bundle to activate the medial rectus. It may also be caused by a lesion of the horizontal gaze center (paramedian pontic reticular formation), which sends afferents to the VI cranial nucleus. Right OIN resulted in adduction paralysis of the right eye and nystagmus of the contralateral eye in abduction, linked to involvement of the left FLM.

Left peripheral facial palsy is a deficit in the function of the ipsilateral facial nerve, reflecting damage to the nerve fibers downstream of the left VIIth nucleus in the facial colliculus, which surround the VI^th nucleus. The FLM, paramedian reticular pontic formation and VI^th nuclei are located in the posterobasal part of the bridge, in an anatomical region measuring less than 10 mm in diameter [11, 12]. The majority of described cases of Fisher’s eight-and-a-half syndrome are caused by ischemic lesions. Cerebral haemorrhages, as in our patient’s case, are less frequent [6, 8]. The outcome in this patient was favorable. This is not always the case, however, where disabling sequelae are possible [5].

Practitioners should be aware of Fischer’s eight-and-a-half syndrome, especially in our context of limited resources, where brain MRI, the gold standard, is not accessible.

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