Motorisch evozierte Potenziale (MEP) des externen urethralen Sphinkters zur Abklärung der neurogenen Inkontinenz querschnittverletzter Patienten

Zusammenfassung

Ziel: Prospektive Studie zur Diagnose neurogener Läsionen somato-motorisch efferenter Nerven des externen urethralen Sphinkters (EUS) mittels motorisch evozierter Potenziale (MEP) und simultaner Urodynamik (UD).

Patienten und Methoden: 9 gesunde Probanden und 33 Patienten (15 × traumatische Rückenmarkverletzung, 14 × Kaudaläsion und 4 × MS) mit neurogener Urin-Inkontinenz wurden neurologisch, urodynamisch und elektrophysiologisch untersucht. Die Evozierung von MEP-Antworten des EUS erfolgte mittels transkranieller (tk) und lumbosakraler (ls) Einzelpuls-Magnetstimulation. Ein Quotient aus tk/ls Latenzzeiten wurde berechnet, um periphere von zentralen Läsionen zu unterscheiden. Simultan zur EMG-Ableitung wurde über einen Druckmesskatheter mit integrierter Oberflächenelektrode die mechanische EUS-Druckantwort registriert.

Resultate: Bei 9 Probanden betrug die spinale Latenz 19,0 ms, die periphere Latenz 4,25 ms und der errechnete Quotient 4,4. Bei den Pat. mit Rückenmarkverletzung fanden sich eine signifikant verlängerte spinale Latenz von 22,7 ms bei normaler peripherer Latenz. Der Quotient lag mit 5,5 über dem Wert der Gesunden; 13 von diesen 15 Pat. litten unter einer neurogenen Inkontinenz. Pat. mit kompletter spinaler Läsion hatten nach tk Stimulation keine ableitbaren EUS-Antworten bei normalen peripheren Werten. Die Pat. mit MS zeigten ebenso deutlich verlängerte spinale Latenzen von 25,5 ms bei normalen peripheren Latenzen und einem Quotienten von 6,0, der auf eine spinale Läsion hinwies. 10 Patienten mit schwerer Kaudaläsion und Urin-Inkontinenz hatten normale spinale Latenzen jedoch verlängerte periphere Latenzen von 6,7 ms, wobei der erniedrigte Quotient von 3,4 einen Schaden der Kaudawurzeln anzeigte. Bei kompletter Kaudaläsion konnten weder spinale noch periphere MEPs des EUS ausgelöst werden. Tk-evozierte mechanische EUS-Druckantworten waren nur bei intakten resp. inkomplett verletzten spinalen und peripheren motorischen Nervenbahnen erhältlich, während solche nach ls Stimulation unabhängig einer spinalen Läsion nur bei Intaktheit oder Teilintegrität der sakralen Cauda equina-Wurzeln vorhanden waren.

Schlussfolgerungen: MEP- und Druck-Ableitungen des EUS erweisen sich als ergänzende und gut tolerierbare diagnostische Untersuchungen zur Abklärung neurogener Inkontinenz. Dabei können spinale von peripheren Läsionen der motorischen Efferenzen zum EUS differenziert werden.

Abstract

Purpose: A prospective study is presented that assessed neurogenic lesions of the somatic motor efferent potentials (MEP) and simultaneously recorded urodynamics (UD).

Materials and Methods: 9 healthy subjects and 33 patients - 15 × spinal cord injury, 14 × cauda equina lesions and 4 × multiple sclerosis (MS) - with neurogenic urinary incontinence were examined by means of urodynamics and electrophysiology. MEP responses from the EUS were evoked after transcranial (tc) and lumbosacral (ls) single pulse magnetic stimulation. A ratio out of tc/ls latencies was calculated to distinguish between central and peripheral lesions. The mechanical EUS pressure responses were recorded simultaneously with the EMG recordings using a microtipp pressure transducer catheter with an integrated bipolar surface electrode.

Results: In 9 healthy subjects the spinal latency was 19.0 ms, the peripheral latency was 4.25 ms and the ratio was 4.4. In patients with spinal cord lesion, spinal latency was significantly delayed (22.7 ms), whereas peripheral latency was normal. The ratio increased to 5.5. Of these 15 patients, 13 suffered from neurogenic incontinence. Patients with a complete spinal lesion showed no EUS responses after tc stimulation, whereas peripheral answers were normally elicitable. Patients with MS showed significantly longer spinal latencies (25.5 ms). The increased ratio of 6.0 indicated a spinal lesion. Of the patients with severe cauda equina lesions and urinary incontinence, 10 had normal spinal latencies, but longer peripheral latencies of 6.7 ms. The ratio of 3.4 indicated a lesion of the sacral caudal roots. In patients with complete cauda injury, neither spinal nor peripheral responses could be evoked. Tc-evoked mechanical pressure responses from the EUS could only be recorded in intact or incompletely injured spinal and peripheral motor nervous pathways, whereas they could be evoked after ls stimulation only in cases with partially preserved sacral caudal roots independent of a spinal lesion.

Conclusions: MEP and evoked pressure responses from the EUS proved to be an additional and well-tolerable diagnostic tool in the assessment of neurogenic incontinence. Spinal and peripheral lesions of the motor efferent pathways to the EUS can thereby be distinguished.

Motorisch evozierte Potenziale - neurogene Inkontinenz - Querschnittverletzung - Urodynamik - externer urethraler Sphinkter

Evoked potential motor - Neurogenic incontinence - Spinal cord injuries - Urodynamics - External urethral sphincter

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1 Diese Arbeit wurde durch den Schweizerischen Nationalfonds (3200052562) sowie durch das International Institute for Research in Paraplegia (P55/99) unterstützt.