In general, every syllable in a spoken language has a vowel at its core. English allows up to three consonant phonemes on either side. So the words a, me, him, and strengths are one-syllable words. Despite varying quite a bit in the presence or absence of consonants, each of these examples has only one vowel.
In spoken English, certain consonants can have vowel-like characteristics. Sounds that are classified as liquids and nasals can function as the core, or nucleus, of a syllable: /l r m n/. When saying the words bottle, flicker, chasm, and button, the consonant may serve as the core of the syllable instead of a vowel.
In speech, vowels and consonants are typically defined by airflow. Vowels allow more airflow than consonants which are defined as constrictions in airflow. In the example of the word hidden (/hhhhhhhhhɪĭiɪĭiɪĭiˈˈˈˈˈˈˈˈˈdddddddddnnnnnnnnn/), aiflow for /n/ is released through the nose allowing an extra syllable.
In cueing, however, handshape 4 does not have any vowel-like quality. It does not resemble a vowel placement and escaping airflow from the nose is not perceptible to the deaf receiver.
Cueing words that end with a syllabic consonants are straightforward. One can cue /hhhhhhhhhɪĭiɪĭiɪĭiˈˈˈˈˈˈˈˈˈdddddddddnnnnnnnnn/ by transitioning from handshape 1 to handshape 4 at the side with no extra movement. There is a problem inherent in the consonant-vowel (handshape-placement) structure of cueing that causes cuers to make a choice.
Take for instance the word lighten. One could easily cue it ending in a syllabic /n/ at the side placement. Now consider the word lightening pronounced with a syllabic consonant as in "I'm considering lightening my hair." If you imaging the word pronounced with three syllables (containing a syllabic /n/), how would it be cued? Unfortunately, in this case, the syllabic /n/ goes to the throat for the following vowel. The word will appear to the deaf consumer as the two-syllable word, lightning. While hearing cuers believe they are cueing an extra syllable with handshape 4, there is nothing about handshape 4 that gives a word an extra syllable. The same problem occurs in a word like tickling. The cuer is forced to add a schwa in these cases to show the extra syllable.
Another issue facing cuers is the fact that /r/ is often regarded as a syllabic consonant, as is ticker tape. For cuers, though this syllable is placed at the mouth giving it a clear status as a syllable with a vowel at its core. The use of the /ɚûrurɚûrurɚûrur/ at the mouth has the schwa built-in and gives some support as a precedent for using a schwa to ensure that syllables are clearly perceived by the receiver.
The issue of whether or not to cue syllabic consonants is somewhat controversial. The decision, of course, cannot be left solely to the ears of hearing people who want to convey what they perceive. Matters of cueing mechanics must also take into account what is perceived (and perceptible) to deaf cuers. The administrators of DailyCues.com currently hold the position that every syllable gets a vowel. So a schwa is needed for words like tickle, hidden, chasm, and lightening.
In the International Phonetic Alphabet (IPA), syllabics are shown with the letter symbol for the phoneme with a special diacritic mark (a small vertical line) written below: n̩ m̩ l̩ r̩.