MYSTERY clouds the footballing future of North Melbourne tagger Ben Jacobs, who is still struggling to pinpoint why he hasn't played in nine months.

In a bid to recover, Jacobs has had a nerve in his neck burnt off, surgery for sinusitis and worn a mouthguard to rectify his sleep apnea by realigning his jaw.

The 27-year-old was injured in a tackle against Brisbane in round 11 last season.

Jacobs suffered whiplash and told a nmfc.com.au podcast he felt "off", and had neck pain.

The important Roo played the following week against Geelong, missed a month, returned for a round 16 win over Gold Coast, but hasn't taken to the field since.

North had a week off after losing to the Cats.

"I sat down with the doctors the Monday of the week leading into the bye, and that's when things weren't really adding up and I was getting worse," Jacobs said.

"The worst part about it was I didn't know what was going on, and I still don't."

What he does know is it all stems back to that tackle.

"I had none of these symptoms before I hit my head (against the Lions), so since then it has been a combination of things," Jacobs said.

"I have had a neck injury … I have just had my head knocked on the ground ... whether that has flared up the jaw, the nerves in the head, the neck ... it is the perfect storm type of thing.

"To say it is one thing, we can't be sure. I can't rule anything out."

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Initially, the diagnosis was Jacobs was dealing with concussion, having experienced fogginess and feeling run down.

Eventually, doctors identified chronic sinusitis as the issue. It was a problem, but not the only problem.

"I did have a sinus operation, and whatever I did have wrong with the sinuses is gone now, but it wasn't the cause of this," Jacobs said.

"I had a little nerve block in the neck, in a nerve that translates to the front of the forehead, and people can get chronic headaches from that, so I burnt that nerve off in the neck.

"It's been a 10 or 11-month process of finding out what's happening and what's wrong."

His sleep apnea has wreaked havoc with his body's rest period.

"You kind of stop breathing a certain amount of times ... normal is like couple of times, but I am like 10 to 12 times," he said.

"Obviously, my head doesn't feel great now, but my body is good. I don't feel like this is going to hamper me in any way long-term."

Jacobs signed a contract last September, keeping him committed to the club until the end of 2020, and remains confident of returning.

"I feel like I can pick it up when I am healthy again," Jacobs said.

"My body hasn't been battered and bruised too much … I feel like I have plenty to give."

Jacobs has played 90 games since first being drafted by Port Adelaide in 2010 with pick No.16.