Cerebral is one of those medical-anatomical adjectives in which we don’t all agree where the main stress should fall. Other similar cases are skeletal, cervical and our own palatal.
What characterizes these derivatives is a clash between two psychophonological principles. One principle is that of maintaining the shape of the stem to which the suffix -al is attached. Just as person gives us personal and option optional etc, so we may expect to treat the suffix as stress-neutral, giving ˈserəbrəl, ˈskelɪtl̩, ˈsɜːvɪkl̩, ˈpælətl̩, all with initial stress. Compare the initial stress of skeleton, cervix, palate.
(Where the stem has three or more syllables, Chomsky and Halle’s ‘Alternating Stess Rule’ moves the initial stress of the stem to penultimate stress in the adjective, as in ˈuniverse – uniˈversal, ˈdialect – diaˈlectal etc. That is irrelevant here.)
The other principle is the Latin stress rule, largely inherited in English, which says that a long vowel in the penultimate, or any vowel followed by two or more consonants, attracts the main stress to that syllable. So ˈhormone gives us horˈmonal, ˈsepulchre seˈpulchral, and so on. But if the penultimate vowel is part of a ‘weak cluster’, i.e. light — having a short vowel, followed by one consonant or none — then the stress goes not on the penultimate but on the antepenultimate, as ˈpyramid – pyˈramidal.
In English as in Latin, to operate the Latin rule it is crucial to know the quantity (length) of the penultimate vowel. But very few people know Latin these days, and even those of us who do may be uncertain about the classical quantity of this or that vowel.
Dentists and anatomists (in BrE at any rate) “know” in some sense that Latin pălātum has a penultimate long vowel, and accordingly pronounce palatal as pəˈleɪtl̩. Phoneticians don’t have this “knowledge”, or “choose” to ignore it, so we pronounce the word as ˈpælətl̩.
The Greek form of skeleton has -λετ-, with a short vowel, which would regularly yield, via Latin, ˈskelɪtl̩; but those who say skɪˈliːtl̩ do not “know” this.
Latin cervix has the stem cervīc-, with a long vowel, and the surgical tradition is to pronounce cervical accordingly as səˈvaɪkl̩; but the pressure of all the hundreds of other adjectives in -ical leads most lay people to prefer ˈsɜːvɪkl̩.
In the case of cerebral, the relevant vowel of Latin cĕrĕbrum is short. The issue here is whether the consonant cluster br is sufficient to ‘make position’, i.e. make the syllable heavy. Clusters with liquids are characteristically uncertain in this regard (which is incidentally the origin of the term ‘liquid’, i.e. ambiguous or uncertain). If we make the syllable heavy we get ceˈrebral, if light ˈcerebral.
You may recognize this Latin word as part of one of the standard examples of tmesis, in the famous half-line from the poet Ennius,
saxō cĕrĕ- commĭnŭit -brum
‘he shattered his br- -ain with a stone’.