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The existence of a brainstem region concerned with micturition has been known since the report of Barrington more than 70 years ago.1 In animals such a pontine micturition centre has been located in the dorsolateral tegmentum of the rostral pons, corresponding to Barrington’s micturition centre,2 but such a centre has not been precisely localised in humans. We describe a patient with presumed rhombencephalitis presenting with urinary retention and present his MRI findings. To our knowledge, this is the first MRI demonstration of a circumscribed lesion related to the putative pontine micturition centre in humans.
A 30 year old man with no history of voiding problems developed high fever, light headedness, frequent urination, and voiding difficulty. One day after onset, urinary retention occurred despite his sensation of needing to void. Two days later, in addition to urinary retention, the patient also had left cheiro-oral dysaesthesia and horizontal diplopia.Prostate examination did not show abnormalities. Urinary retention was managed with an indwelling catheter until 7 days after onset of his symptoms. The patient did not have a history of overdistension of the urinary bladder. Even though all his symptoms began to improve, the patient was referred to our hospital for an evaluation of neurological abnormalities.
Examination 9 days after onset showed mild right horizontal gaze paresis with intact vestibulo-ocular reflex, ipsilateral saccadic pursuit, and hypaesthesia around the left mouth angle and thumb and index finger, suggesting involvement of the right pontine tegmentum. Indeed, in addition to scattered amorphous lesions in the pons and cerebellum, brain MRI (1.5 tesla) showed a discrete lesion in the right upper pontine tegmentum (figure). An MRI of the spinal cord disclosed no abnormal intensity areas. Lumbar puncture yielded CSF with normal cell counts (3/μl) and mildly increased protein (52 mg/dl). Neither oligoclonal bands nor myelin basic protein were present in the CSF; intrathecal IgG synthesis was within the normal range. Serum autoantibody and viral antibody tests did not contribute to diagnosis. A CO2 cystometry with sphincter EMG 3 weeks after onset showed increased bladder volume over 555 ml and atonic cystometrogram (detrusor areflexia), despite the absence of subjective urinary symptoms. Organic obstructive urological disease was radiologically excluded. All neurological and MRI abnormalities cleared by 1 month after onset. One year follow up showed no recurrence of the neurological symptoms.
Based on neurological findings, the patient was thought to have incomplete involvement of the right paramedian pontine reticular formation, smooth pursuit pathway, and medial lemniscus, suggestive of a right pontine tegmental lesion. The association of acute and reversible urinary retention was consistent with a lesion in the rostral portion of the pontine tegmentum.3 Indeed, the MRI with a special focus on the rostral brainstem substantiated our neurological assessment and showed a discrete lesion in the right dorsolateral portion of the upper pontine tegmentum. Other less distinctive lesions in the pons and cerebellum were seen on MRI, but no relevant neurological abnormalities were detected. Simultaneous involvement of the spinal cord was excluded by neurological and radiological examinations. Although the patient was considered to have possible rhombencephalitis, the question of whether it was caused by a direct virus invasion or parainfectious demyelination remains unclear.
In humans, an association between micturition disturbances and brainstem involvement has been suspected on pathological and radiological bases.3 4 Early in 1926, Holman4 documented a relation between micturition disturbance and posterior fossa tumours. Later, a pathological study of brain tumours disclosed a high frequency (63%; 50/79) of voiding difficulties and urinary retention with pontine and fourth ventricle tumours.3 Histological abnormalities were concentrated in the tegmentum of the rostral pons in all such patients.3The locus coeruleus and adjacent neural tissue were more often involved than other nuclei or regions of the pons.3 However, because of the extensive involvement of these tumours, no localised lesions were noted.3 One recent study with MRI on brainstem stroke disclosed similar results.5 Despite numerous reports on the association between multiple sclerosis and micturition disturbances, MRI studies to date have not delineated brainstem lesions specific to the impaired micturition.
In experimental studies, by contrast, Barrington had suggested that in the cat the micturition region was located in the dorsal part of the pontine tegmentum.1 Recent investigators have reported that it can be located more precisely, in the nucleus locus coeruleus, locus coeruleus alpha, or the dorsomedial part of the dorsolateral pontine tegmentum.2 Neurons in the pontine micturition centre may activate the parasympathetic excitatory outflow to the urinary bladder (detrusor), while there also exists a pontine storage centre ventral or lateral to the pontine micturition centre that controls external urethral sphincter function.2 Because our patient had atonic bladder and urinary retention, the pontine micturition centre may have been the main site of brain involvement. Atonic bladder may reflect a “shock” state, as has been documented in some stroke patients. However, Sakakibara et al 5 described three patients with atonic cystometrogram 3 months, 6 months, and 3 years after brainstem stroke, suggesting a prolonged atonic curve as a supranuclear type of parasympathetic pelvic nerve dysfunction.
Griffiths et al reported bilateral lesions of the pontine micturition centre leading to a period of urinary retention lasting from 2 to 9 weeks, whereas lesions located on only one side had no obvious specific effect on lower urinary tract function.2This may be accounted for by bilateral innervation of the spinal parasympathetic nucleus by the pontine micturition centre.2 However, histology verified that only 15% of the right pontine micturition centre was destroyed.2 A recent PET imaging study disclosed that cortical and pontine micturition sites in humans are predominantly on the right side.6 It is therefore possible that extensive involvement of a unilateral pontine micturition centre, especially the right side, may cause transient urinary retention as found in our patient. Another possibility is that the amorphous lesions in the pons could have interrupted outflow pathways from the opposite pontine micturition centre.
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