Electroencephalography and Clinical Neurophysiology, 1978, 4 4 : 7 8 9 - - 7 9 0
789
© Elsevier/North-Holland Scientific Publishers, Ltd.
Technical contribution UPDATE: CHRONIC SPHENOIDAL ELECTRODES J.R. I V E S and P. G L O O R
Montreal Neurological Institute, Department of Neurology and Neurosurgery, McGill University, Montreal, Que. H3A 2B4 (Canada) ( A c c e p t e d for publication: D e c e m b e r 27, 1977)
Since the d e v e l o p m e n t and subsequent publication (Ives and Gloor 1977) of the chronic sphenoidal electrodes, their ongoing use has led to further technical m o d i f i c a t i o n s and i m p o r t a n t clinical benefits, including longer recording periods and b e t t e r quality EEGs. The 0.003 in. diameter single strand of stainless steel wire with a quad teflon coat had one i m p o r t a n t disadvantage. T h e wires tended to fatigue-fracture after t h e y had been left in the patient's jaw for m a n y days (though never failed before 5 days). The standing order to r e m o v e t h e m after 5 days was logistically awkward in s o m e cases as the E E G / s p h e n o i d a l workup of the patient may n o t have been c o m p l e t e d within 5 days; particularly, if a w e e k e n d or a holiday intervened or if further r e d u c t i o n of anticonvulsant medication was necessary. C o m m e r c i a l l y available n o w are new medical grade m u l t i s t r a n d e d wires *" (A) Stranded stainless steel wire: 7 strands (0.002 in./0.05 m m diam.), quad teflon c o a t (overall diameter 0.009 in./0.25 mm), tensile strength 2000 g, cost U.S. $ 6 9 / 1 0 0 ft., part n u m b e r 3 1 6 5 5 7 / 4 4 T . (b) Stranded pure silver wire, 7 strands (0.0031 in./ 0.1 m m diam.), quad teflon coat (overall diameter 0.010 in./0.27 m m ) , tensile strength 350 g, cost U.S. $ 7 7 / 1 0 0 ft., part n u m b e r A G / 4 0 T . It was felt that the 7-stranded wires w o u l d offer b e t t e r p r o t e c t i o n f r o m fatigue than the single stranded wire, and the very high tensile strength (2000 g) of the stainless steel m a d e it the first choice. The stranded stainless steel wire was used extensively in over 100 patients w i t h o u t a single breakage, even though no restriction on length of stay of the electrodes was m a d e (some patients had the sphenoidal wires left in place for over 3 weeks, average 10 days). There was, however, an assembly p r o b l e m with the stranded stainless steel wire in that it was very stiff, making it awkward to handle. * Medwire C o r p o r a t i o n , 121 S o u t h C o l u m b u s Ave, M o u n t Vernon, N.Y. 10533, U.S.A. ** The electrodes were chlorided in a saline bath with a 1.5 V battery for approx.4 h.
An initial trial was m a d e using the stranded silver wire which was very convenient to handle. However, after using these electrodes in over 50 patients, there seemed to be a m a r k e d increase in the n u m b e r of sphenoidal electrodes requiring r e p l a c e m e n t because o f inherent spontaneous, low-frequency noise artefact. Since the electrode material was pure silver, an a t t e m p t was m a d e to silver/silver chloride the stranded silver electrodes prior to assembly ** In over 50 recent recordings, none of the silver/ silver chlorided electrodes has had to be replaced. We feel that the stranded silver sphenoidal electrode after having been silver/silver chlorided, coupled with the assembly and insertion techniques already discussed ( R o v i t et al. 1960; Ives and G l o o r 1977) constitutes an excellent electrode recording system. Sphenoidal electrodes have now b e c o m e a routine procedure on all temporal lobe epileptic patients investigated at the MNI while the nasopharyngeal procedure has mainly been reserved for out-patients. In Table I, the statistics d e m o n s t r a t e the clinical
TABLE I Table reflects the increase in the use of sphenoidal electrodes during equivalent 9 m o n t h periods before and after the d e v e l o p m e n t of the chronic sphenoidal electrode. Total number of EEGs Before chronic sphenoidals After chronic sphenoidals
Number with sphenoidals
Number with nasopharyngeals
2851
83 (2.9%)
22 (0.8%)
3086
281 (9.1%)
22 (0.7%)
790 success and acceptance of these chronic sphenoidal electrodes.
Summary A technical modification in the type of material used in the chronic sphenoidal electrode previously described (Ives and Gloor 1977) has further improved their clinical use and benefit of the EEG work-up of epileptic patients. This procedure has become a routine investigation for all patients with suspected temporal lobe epilepsy at the Montreal Neurological Hospital. R@sum~ Mise au point: dlectrodes spheno'fdales chroniques Une modification technique du type de mat6riel utilisd pour les ~lectrodes spheno'/dales chroniques
J.R. IVES, P. GLOOR prdc~demment d@crites (Ives et Gloor 1977) a encore am~lior~ leur utilisation clinique et favoris~ l'enregistrement des malades ~pileptiques. Ce proc~d~ est utilis4 en routine chez tousles malades suspects d'4pilepsie temporale ~ l'HSpital Neurologique de Montrdal.
References
Ives, J.R. and Gloor, P. New sphenoidal electrode assembly to permit longterm monitoring of the patient's ictal or interictal EEG. Electroenceph. clin. Neurophysiol., 1977, 42: 575--580. Rovit, R.L., Gloor, P. and Henderson, L.R. Temporal lobe epilepsy -- a study using multiple basal electrodes. I. Description of method. Neurochirurgia (Stuttg.), 1960, 3: 5--18.
789
© Elsevier/North-Holland Scientific Publishers, Ltd.
Technical contribution UPDATE: CHRONIC SPHENOIDAL ELECTRODES J.R. I V E S and P. G L O O R
Montreal Neurological Institute, Department of Neurology and Neurosurgery, McGill University, Montreal, Que. H3A 2B4 (Canada) ( A c c e p t e d for publication: D e c e m b e r 27, 1977)
Since the d e v e l o p m e n t and subsequent publication (Ives and Gloor 1977) of the chronic sphenoidal electrodes, their ongoing use has led to further technical m o d i f i c a t i o n s and i m p o r t a n t clinical benefits, including longer recording periods and b e t t e r quality EEGs. The 0.003 in. diameter single strand of stainless steel wire with a quad teflon coat had one i m p o r t a n t disadvantage. T h e wires tended to fatigue-fracture after t h e y had been left in the patient's jaw for m a n y days (though never failed before 5 days). The standing order to r e m o v e t h e m after 5 days was logistically awkward in s o m e cases as the E E G / s p h e n o i d a l workup of the patient may n o t have been c o m p l e t e d within 5 days; particularly, if a w e e k e n d or a holiday intervened or if further r e d u c t i o n of anticonvulsant medication was necessary. C o m m e r c i a l l y available n o w are new medical grade m u l t i s t r a n d e d wires *" (A) Stranded stainless steel wire: 7 strands (0.002 in./0.05 m m diam.), quad teflon c o a t (overall diameter 0.009 in./0.25 mm), tensile strength 2000 g, cost U.S. $ 6 9 / 1 0 0 ft., part n u m b e r 3 1 6 5 5 7 / 4 4 T . (b) Stranded pure silver wire, 7 strands (0.0031 in./ 0.1 m m diam.), quad teflon coat (overall diameter 0.010 in./0.27 m m ) , tensile strength 350 g, cost U.S. $ 7 7 / 1 0 0 ft., part n u m b e r A G / 4 0 T . It was felt that the 7-stranded wires w o u l d offer b e t t e r p r o t e c t i o n f r o m fatigue than the single stranded wire, and the very high tensile strength (2000 g) of the stainless steel m a d e it the first choice. The stranded stainless steel wire was used extensively in over 100 patients w i t h o u t a single breakage, even though no restriction on length of stay of the electrodes was m a d e (some patients had the sphenoidal wires left in place for over 3 weeks, average 10 days). There was, however, an assembly p r o b l e m with the stranded stainless steel wire in that it was very stiff, making it awkward to handle. * Medwire C o r p o r a t i o n , 121 S o u t h C o l u m b u s Ave, M o u n t Vernon, N.Y. 10533, U.S.A. ** The electrodes were chlorided in a saline bath with a 1.5 V battery for approx.4 h.
An initial trial was m a d e using the stranded silver wire which was very convenient to handle. However, after using these electrodes in over 50 patients, there seemed to be a m a r k e d increase in the n u m b e r of sphenoidal electrodes requiring r e p l a c e m e n t because o f inherent spontaneous, low-frequency noise artefact. Since the electrode material was pure silver, an a t t e m p t was m a d e to silver/silver chloride the stranded silver electrodes prior to assembly ** In over 50 recent recordings, none of the silver/ silver chlorided electrodes has had to be replaced. We feel that the stranded silver sphenoidal electrode after having been silver/silver chlorided, coupled with the assembly and insertion techniques already discussed ( R o v i t et al. 1960; Ives and G l o o r 1977) constitutes an excellent electrode recording system. Sphenoidal electrodes have now b e c o m e a routine procedure on all temporal lobe epileptic patients investigated at the MNI while the nasopharyngeal procedure has mainly been reserved for out-patients. In Table I, the statistics d e m o n s t r a t e the clinical
TABLE I Table reflects the increase in the use of sphenoidal electrodes during equivalent 9 m o n t h periods before and after the d e v e l o p m e n t of the chronic sphenoidal electrode. Total number of EEGs Before chronic sphenoidals After chronic sphenoidals
Number with sphenoidals
Number with nasopharyngeals
2851
83 (2.9%)
22 (0.8%)
3086
281 (9.1%)
22 (0.7%)
790 success and acceptance of these chronic sphenoidal electrodes.
Summary A technical modification in the type of material used in the chronic sphenoidal electrode previously described (Ives and Gloor 1977) has further improved their clinical use and benefit of the EEG work-up of epileptic patients. This procedure has become a routine investigation for all patients with suspected temporal lobe epilepsy at the Montreal Neurological Hospital. R@sum~ Mise au point: dlectrodes spheno'fdales chroniques Une modification technique du type de mat6riel utilisd pour les ~lectrodes spheno'/dales chroniques
J.R. IVES, P. GLOOR prdc~demment d@crites (Ives et Gloor 1977) a encore am~lior~ leur utilisation clinique et favoris~ l'enregistrement des malades ~pileptiques. Ce proc~d~ est utilis4 en routine chez tousles malades suspects d'4pilepsie temporale ~ l'HSpital Neurologique de Montrdal.
References
Ives, J.R. and Gloor, P. New sphenoidal electrode assembly to permit longterm monitoring of the patient's ictal or interictal EEG. Electroenceph. clin. Neurophysiol., 1977, 42: 575--580. Rovit, R.L., Gloor, P. and Henderson, L.R. Temporal lobe epilepsy -- a study using multiple basal electrodes. I. Description of method. Neurochirurgia (Stuttg.), 1960, 3: 5--18.
