Brain-stem compression in vertebrobasilar dolichoectasia. A multimodal electrophysiological study

Objective: To evaluate the effects of mechanical compression of the brain-s tem in patients with vertebrobasilar dolichoectasia (VBD). Methods: In the framework of a prospective, observational study that collec ted clinical and laboratory data in patients with VBD, we studied 20 patien ts with compression of the brain-stem due to ectatic, tortuous basilar or v ertebral arteries. Patients with cerebral lesions other than small lacunae in the white matter of the cerebral hemispheres were excluded from the stud y. Patients underwent vestibular and auditory function testing, including b rain-stem auditory evoked potentials (BAEPs), blink reflex (BR), somatosens ory evoked potentials (SEPs), and motor evoked potentials (MEPs). Results: Almost all of the patients complained of auditory or vestibular sy mptoms and none had symptoms or signs of impairment of long tracts or the f acial and trigeminal nerves. The most consistent findings were BR abnormali ties with prolongation of ipsilateral RI latency in cases of compression of the pons (10/16) and prolongation of the R2 and R2c latencies with compres sion of the medulla oblongata (5/15). Subclinical impairment of corticospin al pathways was found in 13 out of 25 instances of compression, and this wa s more frequent with compression of the pons. Abnormal BAEPs or SEPs were l ess frequently encountered, and only in cases with compression of the pons. Conclusions: Neurovascular compression of the brain-stem, even with severe distortion, is seldom associated with overt clinical signs, whereas subclin ical dysfunctions are relatively frequent. The central pathways of the BR a nd the corticospinal pathways are more susceptible to compression than acou stic and sensory pathways. BR, MEP and BAEP data provide a functional evalu ation of the brain-stem and some cranial nerves, which is lacking in imagin g studies. Functional investigations may be useful in the long-term managem ent of these patients, since VBD may be progressive and surgical correction may be required at some stage. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.