Mitochondrial diseases are characterized by reduction in the functions of the intracellular mitochondria, especially of energy metabolism. There are two major genetic causes groups involved; genes in the nuclear DNA and genes in mitochondrial DNA. Clinical manifestations are diverse. Psychiatric, neurologic, muscular and cardiac manifestations are frequently observed; the renal and endocrine systems are often involved, and underlying diabetes is common. It is crucial to have a high index of suspicion for this disease when patients present with manifestations originating from more than one organ, patients showing a maternal inheritance pattern or patients with high serum and/or cerebrospinal fluid lactate levels in order to diagnose this disease properly.
Opalski's syndrome is considered to be a variant of lateral medullary infarction (Wallenberg's syndrome) with ipsilateral hemiplegia. Although dizziness/vertigo or ocular motor abnormalities commonly occur in Wallenberg's syndrome, these abnormalities are scarcely encountered in Opalski's syndrome. In the present study, two patients with Opalski's syndrome experiencing vertigo/dizziness were evaluated by electronystagmography (ENG). The characteristic findings of ENG were as follows: (1) horizontal nystagmus beating toward the contralateral side of the lesion, (2) tonic conjugate deviation to the side of the lesion (case 2), (3) hypometric saccade toward the side of the lesion and hypermetric saccade toward the contralateral side, (4) smooth pursuit was impaired to the ipsilateral side of the lesion, (5) slow phase peak velocities of OKN were reduced bilaterally, while the steady-state velocities were preserved, and (6) impaired visual suppression (VS) of the slow phase of caloric nystagmus on the ipsilateral side. Among these features, (3) and (4) were the most remarkable findings in our patients. In our present cases, the characteristic directional preponderance of the saccadic and smooth-pursuit eye movement disorders was just the reverse of those observed in Wallenberg's syndrome. Several lines of neurophysiological evidence suggest that in Wallenberg's syndrome, the impaired saccadic and smooth-pursuit movements are caused by dysfunction of the caudal fastigial nuclei. In contrast, after experimental lesioning of the posterior vermis (lobules VI and VII), the directional preponderance of the saccadic and smooth-pursuit eye movements is just the opposite. The findings in our cases were consistent with these observations. Consequently, the findings in our case were presumed to be originated from dysfunction of the posterior vermis. As for reduction of the bilateral slow-phase peak velocities of OKN, it appears to be derived from dysfunction of the flocculus/paraflocculus, and reduction of the ipsilateral VS may be derived from dysfunction of the flocculus or nodulus. MRI in our cases revealed lateral medullary infarction, but no lesions in the cerebellum. Therefore, it was assumed that the above ocular motor abnormalities in our cases may have been mainly derived from lesions of the inferior cerebellar peduncle disrupting the climbing fibers from the contralateral inferior olivary nuclei to the posterior vermis, flocculus/paraflocculus, and nodulus.
Multiple sclerosis (MS) is characterized by multiple demyelinations within the central nervous system. It has been reported that patients with MS frequently have abnormal findings of cervical vestibular evoked myogenic potential (cVEMP) and ocular VEMP (oVEMP). We report the case of a patient with MS in whom cVEMP and oVEMP testing was useful for assessment of the lesions in the brainstem and their recovery. A 17-year-old woman presented with the feeling of light-headedness and a dull ache in the temple. MRI showed multiple T2-prolonged lesions, suggestive of demyelinated lesions in the left medulla oblongata, left superior cerebellar peduncle and left cerebellar hemisphere. One month after the MRI assessment, the patient's clinical findings worsened. She was diagnosed as having MS. Prior to the start of medical treatment, VEMP testing was performed. Air-conducted cVEMP showed a normal response to right ear stimulation, but decreased p13-n23 amplitudes and prolonged p13 latency in the left ear. Air-conducted oVEMP showed a normal amplitude, but prolonged N1 and P1 latencies in response to right ear stimulation, while there was no response to left ear stimulation. ABRs were normal. The patient was started on steroid pulse treatment, in response to which every T2-prolonged lesion in the MRI improved. Air-conducted cVEMP responses to left ear stimulation were restored to normal. Air-conducted sound oVEMPs showed normal amplitudes, but still slightly prolonged N1 and P1 latencies in response to right ear stimulation. oVEMP responses to left ear stimulation appeared after the treatment. According to the results of the first cVEMP and oVEMP testing, it was considered that lesions existed in the left MLF, vestibular nucleus and intramedullary vestibular nerve, while these structures on the right side were spared. The results of the testing for VEMPs were compatible with the MRI findings and the course of the MS. VEMP testing seems to be useful in the assessment of MS patients.
Foulage test is a unique stepping test, in which the patient lifts up only his/her heels alternately, at 120 BPM, 60 seconds with the eyes open and 60 seconds with the eyes closed, on a stabilometer. The environed area (A) and total length (L) were measured and the FT value, a new dynamic equilibrium parameter, 120A/L, was calculated. We tried to plot the contact points of the heels to image the equilibrium disorder. We analyzed the variance of these plots to compare the findings between the open-eye and closed-eye condition in 39 Romberg-positive patients. The standard deviation in the closed-eye condition was higher as compared with that in the open-eye condition. The variance was strongly related to the FT value.